1641215367
How to Add Buttons and Accordion in Bootstrap In Hindi
How to add Buttons and Accordion in Bootstrap in Hindi
Chapters
00:00 Welcome to Coding Talkies with Vikas
00:13 Self introduction
00:35 Introduction to the Course
01:05 Scope of this video
01: 57 Bootstrap buttons
02:30 Types of buttons
08:26 Buttons as HTML tags using anchor tags / input text
10:47 Outline buttons
12:08 sizes of buttons
13:33 Disabled state in buttons
14:55 Bootstrap Accordion
18:25 Accordion demo
22:35 Accordion flush
24:00 Always open accordion
27:11 Introduction to Newton School
* Source Code: https://drive.google.com/drive/folders/1-5VSBrAoNwVOe3BG4eihUk3OrsMM-Duz?usp=sharing
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1625778780
Bootstrap Buttons Tutorial Using Bootstrap Framework
Bootstrap Buttons Tutorial Using a Bootstrap Framework.
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Search Box Design Tutorial Using Only HTML and CSS : https://youtu.be/_F4DdlgQX5U
How To Create Website Preloader in HTML and CSS : https://youtu.be/c9tElJYxyxQ
How to Create Simple Registration Form using only HTML and CSS || Sign up Page Design Tutorial : https://youtu.be/Pcrd_ObbScs
#Tutorial #EasyWebCode
#bootstrap #bootstrap framework #bootstrap buttons
1641616950
Ajouter En Python - Comment Ajouter à Une Liste Ou à Un Tableau
Dans cet article, vous découvrirez la .append()méthode en Python. Vous verrez également en quoi .append()diffère des autres méthodes utilisées pour ajouter des éléments aux listes.
Commençons!
Que sont les listes en Python ? Une définition pour les débutants
Un tableau en programmation est une collection ordonnée d'éléments, et tous les éléments doivent être du même type de données.
Cependant, contrairement à d'autres langages de programmation, les tableaux ne sont pas une structure de données intégrée à Python. Au lieu des tableaux traditionnels, Python utilise des listes.
Les listes sont essentiellement des tableaux dynamiques et sont l'une des structures de données les plus courantes et les plus puissantes de Python.
Vous pouvez les considérer comme des conteneurs commandés. Ils stockent et organisent ensemble des données similaires.
Les éléments stockés dans une liste peuvent être de n'importe quel type de données.
Il peut y avoir des listes d'entiers (nombres entiers), des listes de flottants (nombres à virgule flottante), des listes de chaînes (texte) et des listes de tout autre type de données Python intégré.
Bien qu'il soit possible pour les listes de ne contenir que des éléments du même type de données, elles sont plus flexibles que les tableaux traditionnels. Cela signifie qu'il peut y avoir une variété de types de données différents dans la même liste.
Les listes ont 0 ou plusieurs éléments, ce qui signifie qu'il peut également y avoir des listes vides. À l'intérieur d'une liste, il peut également y avoir des valeurs en double.
Les valeurs sont séparées par une virgule et placées entre crochets, [].
Comment créer des listes en Python
Pour créer une nouvelle liste, donnez d'abord un nom à la liste. Ajoutez ensuite l'opérateur d'affectation ( =) et une paire de crochets ouvrants et fermants. A l'intérieur des parenthèses, ajoutez les valeurs que la liste doit contenir.
#create a new list of names
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#print the list to the console
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny']
Comment les listes sont indexées en Python
Les listes maintiennent un ordre pour chaque article.
Chaque élément de la collection a son propre numéro d'index, que vous pouvez utiliser pour accéder à l'élément lui-même.
Les index en Python (et tout autre langage de programmation moderne) commencent à 0 et augmentent pour chaque élément de la liste.
Par exemple, la liste créée précédemment avait 4 valeurs :
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
La première valeur de la liste, "Jimmy", a un indice de 0.
La deuxième valeur de la liste, "Timmy", a un indice de 1.
La troisième valeur de la liste, "Kenny", a un indice de 2.
La quatrième valeur de la liste, "Lenny", a un indice de 3.
Pour accéder à un élément de la liste par son numéro d'index, écrivez d'abord le nom de la liste, puis entre crochets écrivez l'entier de l'index de l'élément.
Par exemple, si vous vouliez accéder à l'élément qui a un index de 2, vous feriez :
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
print(names[2])
#output
#Kenny
Les listes en Python sont modifiables
En Python, lorsque les objets sont mutables , cela signifie que leurs valeurs peuvent être modifiées une fois qu'ils ont été créés.
Les listes sont des objets modifiables, vous pouvez donc les mettre à jour et les modifier après leur création.
Les listes sont également dynamiques, ce qui signifie qu'elles peuvent augmenter et diminuer tout au long de la vie d'un programme.
Des éléments peuvent être supprimés d'une liste existante et de nouveaux éléments peuvent être ajoutés à une liste existante.
Il existe des méthodes intégrées pour ajouter et supprimer des éléments des listes.
Par exemple, pour add articles, il y a les .append(), .insert()et les .extend()méthodes.
Pour supprimer des éléments, il existe les méthodes .remove(), .pop()et .pop(index).
A quoi sert la .append()méthode ?
La .append()méthode ajoute un élément supplémentaire à la fin d'une liste déjà existante.
La syntaxe générale ressemble à ceci :
list_name.append(item)
Décomposons-le :
list_nameest le nom que vous avez donné à la liste..append()est la méthode de liste pour ajouter un élément à la fin delist_name.itemest l'élément individuel spécifié que vous souhaitez ajouter.
Lors de l'utilisation de .append(), la liste d'origine est modifiée. Aucune nouvelle liste n'est créée.
Si vous souhaitez ajouter un nom supplémentaire à la liste créée précédemment, procédez comme suit :
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#add the name Dylan to the end of the list
names.append("Dylan")
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny', 'Dylan']
Quelle est la différence entre les méthodes .append()et .insert()?
La différence entre les deux méthodes est qu'elle .append()ajoute un élément à la fin d'une liste, alors qu'elle .insert()insère et élément à une position spécifiée dans la liste.
Comme vous l'avez vu dans la section précédente, .append()ajoutera l'élément que vous passez comme argument à la fonction toujours à la fin de la liste.
Si vous ne souhaitez pas simplement ajouter des éléments à la fin d'une liste, vous pouvez spécifier la position à laquelle vous souhaitez les ajouter avec .insert().
La syntaxe générale ressemble à ceci :
list_name.insert(position,item)
Décomposons-le :
list_nameest le nom de la liste..insert()est la méthode de liste pour insérer un élément dans une liste.positionest le premier argument de la méthode. C'est toujours un entier - en particulier c'est le numéro d'index de la position où vous voulez que le nouvel élément soit placé.itemest le deuxième argument de la méthode. Ici, vous spécifiez le nouvel élément que vous souhaitez ajouter à la liste.
Par exemple, supposons que vous disposiez de la liste suivante de langages de programmation :
programming_languages = ["JavaScript", "Java", "C++"]
print(programming_languages)
#output
#['JavaScript', 'Java', 'C++']
Si vous vouliez insérer "Python" au début de la liste, en tant que nouvel élément de la liste, vous utiliseriez la .insert()méthode et spécifieriez la position comme 0. (Rappelez-vous que la première valeur d'une liste a toujours un indice de 0.)
programming_languages = ["JavaScript", "Java", "C++"]
programming_languages.insert(0, "Python")
print(programming_languages)
#output
#['Python', 'JavaScript', 'Java', 'C++']
Si vous aviez plutôt voulu que "JavaScript" soit le premier élément de la liste, puis ajoutez "Python" comme nouvel élément, vous spécifieriez la position comme suit1 :
programming_languages = ["JavaScript", "Java", "C++"]
programming_languages.insert(1,"Python")
print(programming_languages)
#output
#['JavaScript', 'Python', 'Java', 'C++']
La .insert()méthode vous donne un peu plus de flexibilité par rapport à la .append()méthode qui ajoute uniquement un nouvel élément à la fin de la liste.
Quelle est la différence entre les méthodes .append()et .extend()?
Que faire si vous souhaitez ajouter plusieurs éléments à une liste à la fois, au lieu de les ajouter un à la fois ?
Vous pouvez utiliser la .append()méthode pour ajouter plusieurs éléments à la fin d'une liste.
Supposons que vous ayez une liste qui ne contient que deux langages de programmation :
programming_languages = ["JavaScript", "Java"]
print(programming_languages)
#output
#['JavaScript', 'Java']
Vous souhaitez ensuite ajouter deux autres langues, à la fin.
Dans ce cas, vous passez une liste contenant les deux nouvelles valeurs que vous souhaitez ajouter, en argument à .append():
programming_languages = ["JavaScript", "Java"]
#add two new items to the end of the list
programming_languages.append(["Python","C++"])
print(programming_languages)
#output
#['JavaScript', 'Java', ['Python', 'C++']]
Si vous regardez de plus près la sortie ci-dessus, ['JavaScript', 'Java', ['Python', 'C++']]vous verrez qu'une nouvelle liste a été ajoutée à la fin de la liste déjà existante.
Donc, .append() ajoute une liste à l'intérieur d'une liste .
Les listes sont des objets, et lorsque vous utilisez .append()pour ajouter une autre liste dans une liste, les nouveaux éléments seront ajoutés en tant qu'objet unique (élément).
Supposons que vous ayez déjà deux listes, comme ceci :
names = ["Jimmy", "Timmy"]
more_names = ["Kenny", "Lenny"]
Et si vous vouliez combiner le contenu des deux listes en une seule, en ajoutant le contenu de more_namesto names?
Lorsque la .append()méthode est utilisée à cette fin, une autre liste est créée à l'intérieur de names:
names = ["Jimmy", "Timmy"]
more_names = ["Kenny", "Lenny"]
#add contents of more_names to names
names.append(more_names)
print(names)
#output
#['Jimmy', 'Timmy', ['Kenny', 'Lenny']]
Donc, .append()ajoute les nouveaux éléments comme une autre liste, en ajoutant l'objet à la fin.
Pour réellement concaténer (ajouter) des listes et combiner tous les éléments d'une liste à une autre , vous devez utiliser la .extend()méthode.
La syntaxe générale ressemble à ceci :
list_name.extend(iterable/other_list_name)
Décomposons-le :
list_nameest le nom de l'une des listes..extend()est la méthode pour ajouter tout le contenu d'une liste à une autre.iterablepeut être n'importe quel itérable tel qu'une autre liste, par exemple,another_list_name. Dans ce cas,another_list_nameest une liste qui sera concaténée aveclist_name, et son contenu sera ajouté un par un à la fin delist_name, en tant qu'éléments séparés.
Ainsi, en reprenant l'exemple précédent, lorsque .append()est remplacé par .extend(), la sortie ressemblera à ceci :
names = ["Jimmy", "Timmy"]
more_names = ["Kenny", "Lenny"]
names.extend(more_names)
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny']
Lorsque nous avons utilisé .extend(), la namesliste s'est allongée et sa longueur a été augmentée de 2.
La façon dont cela .extend()fonctionne est qu'il prend une liste (ou un autre itérable) comme argument, itère sur chaque élément, puis chaque élément de l'itérable est ajouté à la liste.
Il existe une autre différence entre .append()et .extend().
Lorsque vous souhaitez ajouter une chaîne, comme vu précédemment, .append()ajoutez l'élément entier et unique à la fin de la liste :
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#add the name Dylan to the end of the list
names.append("Dylan")
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny', 'Dylan']
Si vous aviez .extend()plutôt l' habitude d'ajouter une chaîne à la fin d'une liste, chaque caractère de la chaîne serait ajouté en tant qu'élément individuel à la liste.
C'est parce que les chaînes sont un itérable et .extend()qu'elles itèrent sur l'argument itérable qui lui est transmis.
Ainsi, l'exemple ci-dessus ressemblerait à ceci :
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#pass a string(iterable) to .extend()
names.extend("Dylan")
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny', 'D', 'y', 'l', 'a', 'n']
Conclusion
En résumé, la .append()méthode est utilisée pour ajouter un élément à la fin d'une liste existante, sans créer de nouvelle liste.
Lorsqu'il est utilisé pour ajouter une liste à une autre liste, il crée une liste dans une liste.
Si vous souhaitez en savoir plus sur Python, consultez la certification Python de freeCodeCamp . Vous commencerez à apprendre de manière interactive et conviviale pour les débutants. Vous construirez également cinq projets à la fin pour mettre en pratique ce que vous avez appris.
Merci d'avoir lu et bon codage!
Link: https://www.freecodecamp.org/news/append-in-python-how-to-append-to-a-list-or-an-array/
1666082925
How to Create Arrays in Python
In this tutorial, you'll know the basics of how to create arrays in Python using the array module. Learn how to use Python arrays. You'll see how to define them and the different methods commonly used for performing operations on them.
This tutorialvideo on 'Arrays in Python' will help you establish a strong hold on all the fundamentals in python programming language. Below are the topics covered in this video:
1:15 What is an array?
2:53 Is python list same as an array?
3:48 How to create arrays in python?
7:19 Accessing array elements
9:59 Basic array operations
- 10:33 Finding the length of an array
- 11:44 Adding Elements
- 15:06 Removing elements
- 18:32 Array concatenation
- 20:59 Slicing
- 23:26 Looping
Python Array Tutorial – Define, Index, Methods
In this article, you'll learn how to use Python arrays. You'll see how to define them and the different methods commonly used for performing operations on them.
The artcile covers arrays that you create by importing the array module. We won't cover NumPy arrays here.
Table of Contents
- Introduction to Arrays
- The differences between Lists and Arrays
- When to use arrays
- How to use arrays
- Define arrays
- Find the length of arrays
- Array indexing
- Search through arrays
- Loop through arrays
- Slice an array
- Array methods for performing operations
- Change an existing value
- Add a new value
- Remove a value
- Conclusion
Let's get started!
What are Python Arrays?
Arrays are a fundamental data structure, and an important part of most programming languages. In Python, they are containers which are able to store more than one item at the same time.
Specifically, they are an ordered collection of elements with every value being of the same data type. That is the most important thing to remember about Python arrays - the fact that they can only hold a sequence of multiple items that are of the same type.
What's the Difference between Python Lists and Python Arrays?
Lists are one of the most common data structures in Python, and a core part of the language.
Lists and arrays behave similarly.
Just like arrays, lists are an ordered sequence of elements.
They are also mutable and not fixed in size, which means they can grow and shrink throughout the life of the program. Items can be added and removed, making them very flexible to work with.
However, lists and arrays are not the same thing.
Lists store items that are of various data types. This means that a list can contain integers, floating point numbers, strings, or any other Python data type, at the same time. That is not the case with arrays.
As mentioned in the section above, arrays store only items that are of the same single data type. There are arrays that contain only integers, or only floating point numbers, or only any other Python data type you want to use.
When to Use Python Arrays
Lists are built into the Python programming language, whereas arrays aren't. Arrays are not a built-in data structure, and therefore need to be imported via the array module in order to be used.
Arrays of the array module are a thin wrapper over C arrays, and are useful when you want to work with homogeneous data.
They are also more compact and take up less memory and space which makes them more size efficient compared to lists.
If you want to perform mathematical calculations, then you should use NumPy arrays by importing the NumPy package. Besides that, you should just use Python arrays when you really need to, as lists work in a similar way and are more flexible to work with.
How to Use Arrays in Python
In order to create Python arrays, you'll first have to import the array module which contains all the necassary functions.
There are three ways you can import the array module:
- By using
import arrayat the top of the file. This includes the modulearray. You would then go on to create an array usingarray.array().
import array
#how you would create an array
array.array()- Instead of having to type
array.array()all the time, you could useimport array as arrat the top of the file, instead ofimport arrayalone. You would then create an array by typingarr.array(). Thearracts as an alias name, with the array constructor then immediately following it.
import array as arr
#how you would create an array
arr.array()- Lastly, you could also use
from array import *, with*importing all the functionalities available. You would then create an array by writing thearray()constructor alone.
from array import *
#how you would create an array
array()How to Define Arrays in Python
Once you've imported the array module, you can then go on to define a Python array.
The general syntax for creating an array looks like this:
variable_name = array(typecode,[elements])Let's break it down:
variable_namewould be the name of the array.- The
typecodespecifies what kind of elements would be stored in the array. Whether it would be an array of integers, an array of floats or an array of any other Python data type. Remember that all elements should be of the same data type. - Inside square brackets you mention the
elementsthat would be stored in the array, with each element being separated by a comma. You can also create an empty array by just writingvariable_name = array(typecode)alone, without any elements.
Below is a typecode table, with the different typecodes that can be used with the different data types when defining Python arrays:
| TYPECODE | C TYPE | PYTHON TYPE | SIZE |
|---|---|---|---|
| 'b' | signed char | int | 1 |
| 'B' | unsigned char | int | 1 |
| 'u' | wchar_t | Unicode character | 2 |
| 'h' | signed short | int | 2 |
| 'H' | unsigned short | int | 2 |
| 'i' | signed int | int | 2 |
| 'I' | unsigned int | int | 2 |
| 'l' | signed long | int | 4 |
| 'L' | unsigned long | int | 4 |
| 'q' | signed long long | int | 8 |
| 'Q' | unsigned long long | int | 8 |
| 'f' | float | float | 4 |
| 'd' | double | float | 8 |
Tying everything together, here is an example of how you would define an array in Python:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers)
#output
#array('i', [10, 20, 30])Let's break it down:
- First we included the array module, in this case with
import array as arr. - Then, we created a
numbersarray. - We used
arr.array()because ofimport array as arr. - Inside the
array()constructor, we first includedi, for signed integer. Signed integer means that the array can include positive and negative values. Unsigned integer, withHfor example, would mean that no negative values are allowed. - Lastly, we included the values to be stored in the array in square brackets.
Keep in mind that if you tried to include values that were not of i typecode, meaning they were not integer values, you would get an error:
import array as arr
numbers = arr.array('i',[10.0,20,30])
print(numbers)
#output
#Traceback (most recent call last):
# File "/Users/dionysialemonaki/python_articles/demo.py", line 14, in <module>
# numbers = arr.array('i',[10.0,20,30])
#TypeError: 'float' object cannot be interpreted as an integerIn the example above, I tried to include a floating point number in the array. I got an error because this is meant to be an integer array only.
Another way to create an array is the following:
from array import *
#an array of floating point values
numbers = array('d',[10.0,20.0,30.0])
print(numbers)
#output
#array('d', [10.0, 20.0, 30.0])The example above imported the array module via from array import * and created an array numbers of float data type. This means that it holds only floating point numbers, which is specified with the 'd' typecode.
How to Find the Length of an Array in Python
To find out the exact number of elements contained in an array, use the built-in len() method.
It will return the integer number that is equal to the total number of elements in the array you specify.
import array as arr
numbers = arr.array('i',[10,20,30])
print(len(numbers))
#output
# 3In the example above, the array contained three elements – 10, 20, 30 – so the length of numbers is 3.
Array Indexing and How to Access Individual Items in an Array in Python
Each item in an array has a specific address. Individual items are accessed by referencing their index number.
Indexing in Python, and in all programming languages and computing in general, starts at 0. It is important to remember that counting starts at 0 and not at 1.
To access an element, you first write the name of the array followed by square brackets. Inside the square brackets you include the item's index number.
The general syntax would look something like this:
array_name[index_value_of_item]Here is how you would access each individual element in an array:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers[0]) # gets the 1st element
print(numbers[1]) # gets the 2nd element
print(numbers[2]) # gets the 3rd element
#output
#10
#20
#30Remember that the index value of the last element of an array is always one less than the length of the array. Where n is the length of the array, n - 1 will be the index value of the last item.
Note that you can also access each individual element using negative indexing.
With negative indexing, the last element would have an index of -1, the second to last element would have an index of -2, and so on.
Here is how you would get each item in an array using that method:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers[-1]) #gets last item
print(numbers[-2]) #gets second to last item
print(numbers[-3]) #gets first item
#output
#30
#20
#10How to Search Through an Array in Python
You can find out an element's index number by using the index() method.
You pass the value of the element being searched as the argument to the method, and the element's index number is returned.
import array as arr
numbers = arr.array('i',[10,20,30])
#search for the index of the value 10
print(numbers.index(10))
#output
#0If there is more than one element with the same value, the index of the first instance of the value will be returned:
import array as arr
numbers = arr.array('i',[10,20,30,10,20,30])
#search for the index of the value 10
#will return the index number of the first instance of the value 10
print(numbers.index(10))
#output
#0How to Loop through an Array in Python
You've seen how to access each individual element in an array and print it out on its own.
You've also seen how to print the array, using the print() method. That method gives the following result:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers)
#output
#array('i', [10, 20, 30])What if you want to print each value one by one?
This is where a loop comes in handy. You can loop through the array and print out each value, one-by-one, with each loop iteration.
For this you can use a simple for loop:
import array as arr
numbers = arr.array('i',[10,20,30])
for number in numbers:
print(number)
#output
#10
#20
#30You could also use the range() function, and pass the len() method as its parameter. This would give the same result as above:
import array as arr
values = arr.array('i',[10,20,30])
#prints each individual value in the array
for value in range(len(values)):
print(values[value])
#output
#10
#20
#30How to Slice an Array in Python
To access a specific range of values inside the array, use the slicing operator, which is a colon :.
When using the slicing operator and you only include one value, the counting starts from 0 by default. It gets the first item, and goes up to but not including the index number you specify.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#get the values 10 and 20 only
print(numbers[:2]) #first to second position
#output
#array('i', [10, 20])When you pass two numbers as arguments, you specify a range of numbers. In this case, the counting starts at the position of the first number in the range, and up to but not including the second one:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#get the values 20 and 30 only
print(numbers[1:3]) #second to third position
#output
#rray('i', [20, 30])Methods For Performing Operations on Arrays in Python
Arrays are mutable, which means they are changeable. You can change the value of the different items, add new ones, or remove any you don't want in your program anymore.
Let's see some of the most commonly used methods which are used for performing operations on arrays.
How to Change the Value of an Item in an Array
You can change the value of a specific element by speficying its position and assigning it a new value:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#change the first element
#change it from having a value of 10 to having a value of 40
numbers[0] = 40
print(numbers)
#output
#array('i', [40, 20, 30])How to Add a New Value to an Array
To add one single value at the end of an array, use the append() method:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integer 40 to the end of numbers
numbers.append(40)
print(numbers)
#output
#array('i', [10, 20, 30, 40])Be aware that the new item you add needs to be the same data type as the rest of the items in the array.
Look what happens when I try to add a float to an array of integers:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integer 40 to the end of numbers
numbers.append(40.0)
print(numbers)
#output
#Traceback (most recent call last):
# File "/Users/dionysialemonaki/python_articles/demo.py", line 19, in <module>
# numbers.append(40.0)
#TypeError: 'float' object cannot be interpreted as an integerBut what if you want to add more than one value to the end an array?
Use the extend() method, which takes an iterable (such as a list of items) as an argument. Again, make sure that the new items are all the same data type.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integers 40,50,60 to the end of numbers
#The numbers need to be enclosed in square brackets
numbers.extend([40,50,60])
print(numbers)
#output
#array('i', [10, 20, 30, 40, 50, 60])And what if you don't want to add an item to the end of an array? Use the insert() method, to add an item at a specific position.
The insert() function takes two arguments: the index number of the position the new element will be inserted, and the value of the new element.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integer 40 in the first position
#remember indexing starts at 0
numbers.insert(0,40)
print(numbers)
#output
#array('i', [40, 10, 20, 30])How to Remove a Value from an Array
To remove an element from an array, use the remove() method and include the value as an argument to the method.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
numbers.remove(10)
print(numbers)
#output
#array('i', [20, 30])With remove(), only the first instance of the value you pass as an argument will be removed.
See what happens when there are more than one identical values:
import array as arr
#original array
numbers = arr.array('i',[10,20,30,10,20])
numbers.remove(10)
print(numbers)
#output
#array('i', [20, 30, 10, 20])Only the first occurence of 10 is removed.
You can also use the pop() method, and specify the position of the element to be removed:
import array as arr
#original array
numbers = arr.array('i',[10,20,30,10,20])
#remove the first instance of 10
numbers.pop(0)
print(numbers)
#output
#array('i', [20, 30, 10, 20])Conclusion
And there you have it - you now know the basics of how to create arrays in Python using the array module. Hopefully you found this guide helpful.
Thanks for reading and happy coding!
#python #programming
1670560264
Understanding Arrays in Python
Learn how to use Python arrays. Create arrays in Python using the array module. You'll see how to define them and the different methods commonly used for performing operations on them.
The artcile covers arrays that you create by importing the array module. We won't cover NumPy arrays here.
Table of Contents
- Introduction to Arrays
- The differences between Lists and Arrays
- When to use arrays
- How to use arrays
- Define arrays
- Find the length of arrays
- Array indexing
- Search through arrays
- Loop through arrays
- Slice an array
- Array methods for performing operations
- Change an existing value
- Add a new value
- Remove a value
- Conclusion
Let's get started!
What are Python Arrays?
Arrays are a fundamental data structure, and an important part of most programming languages. In Python, they are containers which are able to store more than one item at the same time.
Specifically, they are an ordered collection of elements with every value being of the same data type. That is the most important thing to remember about Python arrays - the fact that they can only hold a sequence of multiple items that are of the same type.
What's the Difference between Python Lists and Python Arrays?
Lists are one of the most common data structures in Python, and a core part of the language.
Lists and arrays behave similarly.
Just like arrays, lists are an ordered sequence of elements.
They are also mutable and not fixed in size, which means they can grow and shrink throughout the life of the program. Items can be added and removed, making them very flexible to work with.
However, lists and arrays are not the same thing.
Lists store items that are of various data types. This means that a list can contain integers, floating point numbers, strings, or any other Python data type, at the same time. That is not the case with arrays.
As mentioned in the section above, arrays store only items that are of the same single data type. There are arrays that contain only integers, or only floating point numbers, or only any other Python data type you want to use.
When to Use Python Arrays
Lists are built into the Python programming language, whereas arrays aren't. Arrays are not a built-in data structure, and therefore need to be imported via the array module in order to be used.
Arrays of the array module are a thin wrapper over C arrays, and are useful when you want to work with homogeneous data.
They are also more compact and take up less memory and space which makes them more size efficient compared to lists.
If you want to perform mathematical calculations, then you should use NumPy arrays by importing the NumPy package. Besides that, you should just use Python arrays when you really need to, as lists work in a similar way and are more flexible to work with.
How to Use Arrays in Python
In order to create Python arrays, you'll first have to import the array module which contains all the necassary functions.
There are three ways you can import the array module:
- By using
import arrayat the top of the file. This includes the modulearray. You would then go on to create an array usingarray.array().
import array
#how you would create an array
array.array()
- Instead of having to type
array.array()all the time, you could useimport array as arrat the top of the file, instead ofimport arrayalone. You would then create an array by typingarr.array(). Thearracts as an alias name, with the array constructor then immediately following it.
import array as arr
#how you would create an array
arr.array()
- Lastly, you could also use
from array import *, with*importing all the functionalities available. You would then create an array by writing thearray()constructor alone.
from array import *
#how you would create an array
array()
How to Define Arrays in Python
Once you've imported the array module, you can then go on to define a Python array.
The general syntax for creating an array looks like this:
variable_name = array(typecode,[elements])
Let's break it down:
variable_namewould be the name of the array.- The
typecodespecifies what kind of elements would be stored in the array. Whether it would be an array of integers, an array of floats or an array of any other Python data type. Remember that all elements should be of the same data type. - Inside square brackets you mention the
elementsthat would be stored in the array, with each element being separated by a comma. You can also create an empty array by just writingvariable_name = array(typecode)alone, without any elements.
Below is a typecode table, with the different typecodes that can be used with the different data types when defining Python arrays:
| TYPECODE | C TYPE | PYTHON TYPE | SIZE |
|---|---|---|---|
| 'b' | signed char | int | 1 |
| 'B' | unsigned char | int | 1 |
| 'u' | wchar_t | Unicode character | 2 |
| 'h' | signed short | int | 2 |
| 'H' | unsigned short | int | 2 |
| 'i' | signed int | int | 2 |
| 'I' | unsigned int | int | 2 |
| 'l' | signed long | int | 4 |
| 'L' | unsigned long | int | 4 |
| 'q' | signed long long | int | 8 |
| 'Q' | unsigned long long | int | 8 |
| 'f' | float | float | 4 |
| 'd' | double | float | 8 |
Tying everything together, here is an example of how you would define an array in Python:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers)
#output
#array('i', [10, 20, 30])
Let's break it down:
- First we included the array module, in this case with
import array as arr. - Then, we created a
numbersarray. - We used
arr.array()because ofimport array as arr. - Inside the
array()constructor, we first includedi, for signed integer. Signed integer means that the array can include positive and negative values. Unsigned integer, withHfor example, would mean that no negative values are allowed. - Lastly, we included the values to be stored in the array in square brackets.
Keep in mind that if you tried to include values that were not of i typecode, meaning they were not integer values, you would get an error:
import array as arr
numbers = arr.array('i',[10.0,20,30])
print(numbers)
#output
#Traceback (most recent call last):
# File "/Users/dionysialemonaki/python_articles/demo.py", line 14, in <module>
# numbers = arr.array('i',[10.0,20,30])
#TypeError: 'float' object cannot be interpreted as an integer
In the example above, I tried to include a floating point number in the array. I got an error because this is meant to be an integer array only.
Another way to create an array is the following:
from array import *
#an array of floating point values
numbers = array('d',[10.0,20.0,30.0])
print(numbers)
#output
#array('d', [10.0, 20.0, 30.0])
The example above imported the array module via from array import * and created an array numbers of float data type. This means that it holds only floating point numbers, which is specified with the 'd' typecode.
How to Find the Length of an Array in Python
To find out the exact number of elements contained in an array, use the built-in len() method.
It will return the integer number that is equal to the total number of elements in the array you specify.
import array as arr
numbers = arr.array('i',[10,20,30])
print(len(numbers))
#output
# 3
In the example above, the array contained three elements – 10, 20, 30 – so the length of numbers is 3.
Array Indexing and How to Access Individual Items in an Array in Python
Each item in an array has a specific address. Individual items are accessed by referencing their index number.
Indexing in Python, and in all programming languages and computing in general, starts at 0. It is important to remember that counting starts at 0 and not at 1.
To access an element, you first write the name of the array followed by square brackets. Inside the square brackets you include the item's index number.
The general syntax would look something like this:
array_name[index_value_of_item]
Here is how you would access each individual element in an array:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers[0]) # gets the 1st element
print(numbers[1]) # gets the 2nd element
print(numbers[2]) # gets the 3rd element
#output
#10
#20
#30
Remember that the index value of the last element of an array is always one less than the length of the array. Where n is the length of the array, n - 1 will be the index value of the last item.
Note that you can also access each individual element using negative indexing.
With negative indexing, the last element would have an index of -1, the second to last element would have an index of -2, and so on.
Here is how you would get each item in an array using that method:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers[-1]) #gets last item
print(numbers[-2]) #gets second to last item
print(numbers[-3]) #gets first item
#output
#30
#20
#10
How to Search Through an Array in Python
You can find out an element's index number by using the index() method.
You pass the value of the element being searched as the argument to the method, and the element's index number is returned.
import array as arr
numbers = arr.array('i',[10,20,30])
#search for the index of the value 10
print(numbers.index(10))
#output
#0
If there is more than one element with the same value, the index of the first instance of the value will be returned:
import array as arr
numbers = arr.array('i',[10,20,30,10,20,30])
#search for the index of the value 10
#will return the index number of the first instance of the value 10
print(numbers.index(10))
#output
#0
How to Loop through an Array in Python
You've seen how to access each individual element in an array and print it out on its own.
You've also seen how to print the array, using the print() method. That method gives the following result:
import array as arr
numbers = arr.array('i',[10,20,30])
print(numbers)
#output
#array('i', [10, 20, 30])
What if you want to print each value one by one?
This is where a loop comes in handy. You can loop through the array and print out each value, one-by-one, with each loop iteration.
For this you can use a simple for loop:
import array as arr
numbers = arr.array('i',[10,20,30])
for number in numbers:
print(number)
#output
#10
#20
#30
You could also use the range() function, and pass the len() method as its parameter. This would give the same result as above:
import array as arr
values = arr.array('i',[10,20,30])
#prints each individual value in the array
for value in range(len(values)):
print(values[value])
#output
#10
#20
#30
How to Slice an Array in Python
To access a specific range of values inside the array, use the slicing operator, which is a colon :.
When using the slicing operator and you only include one value, the counting starts from 0 by default. It gets the first item, and goes up to but not including the index number you specify.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#get the values 10 and 20 only
print(numbers[:2]) #first to second position
#output
#array('i', [10, 20])
When you pass two numbers as arguments, you specify a range of numbers. In this case, the counting starts at the position of the first number in the range, and up to but not including the second one:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#get the values 20 and 30 only
print(numbers[1:3]) #second to third position
#output
#rray('i', [20, 30])
Methods For Performing Operations on Arrays in Python
Arrays are mutable, which means they are changeable. You can change the value of the different items, add new ones, or remove any you don't want in your program anymore.
Let's see some of the most commonly used methods which are used for performing operations on arrays.
How to Change the Value of an Item in an Array
You can change the value of a specific element by speficying its position and assigning it a new value:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#change the first element
#change it from having a value of 10 to having a value of 40
numbers[0] = 40
print(numbers)
#output
#array('i', [40, 20, 30])
How to Add a New Value to an Array
To add one single value at the end of an array, use the append() method:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integer 40 to the end of numbers
numbers.append(40)
print(numbers)
#output
#array('i', [10, 20, 30, 40])
Be aware that the new item you add needs to be the same data type as the rest of the items in the array.
Look what happens when I try to add a float to an array of integers:
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integer 40 to the end of numbers
numbers.append(40.0)
print(numbers)
#output
#Traceback (most recent call last):
# File "/Users/dionysialemonaki/python_articles/demo.py", line 19, in <module>
# numbers.append(40.0)
#TypeError: 'float' object cannot be interpreted as an integer
But what if you want to add more than one value to the end an array?
Use the extend() method, which takes an iterable (such as a list of items) as an argument. Again, make sure that the new items are all the same data type.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integers 40,50,60 to the end of numbers
#The numbers need to be enclosed in square brackets
numbers.extend([40,50,60])
print(numbers)
#output
#array('i', [10, 20, 30, 40, 50, 60])
And what if you don't want to add an item to the end of an array? Use the insert() method, to add an item at a specific position.
The insert() function takes two arguments: the index number of the position the new element will be inserted, and the value of the new element.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
#add the integer 40 in the first position
#remember indexing starts at 0
numbers.insert(0,40)
print(numbers)
#output
#array('i', [40, 10, 20, 30])
How to Remove a Value from an Array
To remove an element from an array, use the remove() method and include the value as an argument to the method.
import array as arr
#original array
numbers = arr.array('i',[10,20,30])
numbers.remove(10)
print(numbers)
#output
#array('i', [20, 30])
With remove(), only the first instance of the value you pass as an argument will be removed.
See what happens when there are more than one identical values:
import array as arr
#original array
numbers = arr.array('i',[10,20,30,10,20])
numbers.remove(10)
print(numbers)
#output
#array('i', [20, 30, 10, 20])
Only the first occurence of 10 is removed.
You can also use the pop() method, and specify the position of the element to be removed:
import array as arr
#original array
numbers = arr.array('i',[10,20,30,10,20])
#remove the first instance of 10
numbers.pop(0)
print(numbers)
#output
#array('i', [20, 30, 10, 20])
Conclusion
And there you have it - you now know the basics of how to create arrays in Python using the array module. Hopefully you found this guide helpful.
You'll start from the basics and learn in an interacitve and beginner-friendly way. You'll also build five projects at the end to put into practice and help reinforce what you learned.
Thanks for reading and happy coding!
Original article source at https://www.freecodecamp.org
#python
1641884883
Como anexar A Uma Lista Ou Matriz Em Python Como Um Profissional
Neste artigo, você aprenderá sobre o .append()método em Python. Você também verá como .append()difere de outros métodos usados para adicionar elementos a listas.
Vamos começar!
O que são listas em Python? Uma definição para iniciantes
Uma matriz na programação é uma coleção ordenada de itens e todos os itens precisam ser do mesmo tipo de dados.
No entanto, ao contrário de outras linguagens de programação, os arrays não são uma estrutura de dados embutida no Python. Em vez de arrays tradicionais, o Python usa listas.
Listas são essencialmente arrays dinâmicos e são uma das estruturas de dados mais comuns e poderosas em Python.
Você pode pensar neles como contêineres ordenados. Eles armazenam e organizam tipos semelhantes de dados relacionados juntos.
Os elementos armazenados em uma lista podem ser de qualquer tipo de dados.
Pode haver listas de inteiros (números inteiros), listas de floats (números de ponto flutuante), listas de strings (texto) e listas de qualquer outro tipo de dados interno do Python.
Embora seja possível que as listas contenham apenas itens do mesmo tipo de dados, elas são mais flexíveis do que as matrizes tradicionais. Isso significa que pode haver uma variedade de tipos de dados diferentes dentro da mesma lista.
As listas têm 0 ou mais itens, o que significa que também pode haver listas vazias. Dentro de uma lista também pode haver valores duplicados.
Os valores são separados por uma vírgula e colocados entre colchetes, [].
Como criar listas em Python
Para criar uma nova lista, primeiro dê um nome à lista. Em seguida, adicione o operador de atribuição ( =) e um par de colchetes de abertura e fechamento. Dentro dos colchetes, adicione os valores que você deseja que a lista contenha.
#create a new list of names
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#print the list to the console
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny']
Como as listas são indexadas em Python
As listas mantêm uma ordem para cada item.
Cada item na coleção tem seu próprio número de índice, que você pode usar para acessar o próprio item.
Índices em Python (e em qualquer outra linguagem de programação moderna) começam em 0 e aumentam para cada item da lista.
Por exemplo, a lista criada anteriormente tinha 4 valores:
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
O primeiro valor na lista, "Jimmy", tem um índice de 0.
O segundo valor na lista, "Timmy", tem um índice de 1.
O terceiro valor na lista, "Kenny", tem um índice de 2.
O quarto valor na lista, "Lenny", tem um índice de 3.
Para acessar um elemento na lista por seu número de índice, primeiro escreva o nome da lista, depois entre colchetes escreva o inteiro do índice do elemento.
Por exemplo, se você quisesse acessar o elemento que tem um índice de 2, você faria:
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
print(names[2])
#output
#Kenny
Listas em Python são mutáveis
Em Python, quando os objetos são mutáveis , significa que seus valores podem ser alterados depois de criados.
As listas são objetos mutáveis, portanto, você pode atualizá-las e alterá-las depois de criadas.
As listas também são dinâmicas, o que significa que podem crescer e diminuir ao longo da vida de um programa.
Os itens podem ser removidos de uma lista existente e novos itens podem ser adicionados a uma lista existente.
Existem métodos internos para adicionar e remover itens de listas.
Por exemplo, para add itens, há as .append(), .insert()e .extend()métodos.
Para remove itens, há as .remove(), .pop()e .pop(index)métodos.
O que o .append()método faz?
O .append()método adiciona um elemento adicional ao final de uma lista já existente.
A sintaxe geral se parece com isso:
list_name.append(item)
Vamos decompô-lo:
list_nameé o nome que você deu à lista..append()é o método de lista para adicionar um item ao final delist_name.itemé o item individual especificado que você deseja adicionar.
Ao usar .append(), a lista original é modificada. Nenhuma nova lista é criada.
Se você quiser adicionar um nome extra à lista criada anteriormente, faça o seguinte:
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#add the name Dylan to the end of the list
names.append("Dylan")
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny', 'Dylan']
Qual é a diferença entre os métodos .append()e .insert()?
A diferença entre os dois métodos é que .append()adiciona um item ao final de uma lista, enquanto .insert()insere um item em uma posição especificada na lista.
Como você viu na seção anterior, .append()irá adicionar o item que você passar como argumento para a função sempre no final da lista.
Se você não quiser apenas adicionar itens ao final de uma lista, poderá especificar a posição com a qual deseja adicioná-los .insert().
A sintaxe geral fica assim:
list_name.insert(position,item)
Vamos decompô-lo:
list_nameé o nome da lista..insert()é o método de lista para inserir um item em uma lista.positioné o primeiro argumento para o método. É sempre um número inteiro - especificamente é o número de índice da posição onde você deseja que o novo item seja colocado.itemé o segundo argumento para o método. Aqui você especifica o novo item que deseja adicionar à lista.
Por exemplo, digamos que você tenha a seguinte lista de linguagens de programação:
programming_languages = ["JavaScript", "Java", "C++"]
print(programming_languages)
#output
#['JavaScript', 'Java', 'C++']
Se você quisesse inserir "Python" no início da lista, como um novo item da lista, você usaria o .insert()método e especificaria a posição como 0. (Lembre-se de que o primeiro valor em uma lista sempre tem um índice de 0.)
programming_languages = ["JavaScript", "Java", "C++"]
programming_languages.insert(0, "Python")
print(programming_languages)
#output
#['Python', 'JavaScript', 'Java', 'C++']
Se, em vez disso, você quisesse que "JavaScript" fosse o primeiro item da lista e, em seguida, adicionasse "Python" como o novo item, você especificaria a posição como 1:
programming_languages = ["JavaScript", "Java", "C++"]
programming_languages.insert(1,"Python")
print(programming_languages)
#output
#['JavaScript', 'Python', 'Java', 'C++']
O .insert()método oferece um pouco mais de flexibilidade em comparação com o .append()método que apenas adiciona um novo item ao final da lista.
Qual é a diferença entre os métodos .append()e .extend()?
E se você quiser adicionar mais de um item a uma lista de uma só vez, em vez de adicioná-los um de cada vez?
Você pode usar o .append()método para adicionar mais de um item ao final de uma lista.
Digamos que você tenha uma lista que contém apenas duas linguagens de programação:
programming_languages = ["JavaScript", "Java"]
print(programming_languages)
#output
#['JavaScript', 'Java']
Você então deseja adicionar mais dois idiomas, no final dele.
Nesse caso, você passa uma lista contendo os dois novos valores que deseja adicionar, como argumento para .append():
programming_languages = ["JavaScript", "Java"]
#add two new items to the end of the list
programming_languages.append(["Python","C++"])
print(programming_languages)
#output
#['JavaScript', 'Java', ['Python', 'C++']]
Se você observar mais de perto a saída acima, ['JavaScript', 'Java', ['Python', 'C++']], verá que uma nova lista foi adicionada ao final da lista já existente.
Então, .append() adiciona uma lista dentro de uma lista .
Listas são objetos, e quando você usa .append()para adicionar outra lista em uma lista, os novos itens serão adicionados como um único objeto (item).
Digamos que você já tenha duas listas, assim:
names = ["Jimmy", "Timmy"]
more_names = ["Kenny", "Lenny"]
E se você quiser combinar o conteúdo de ambas as listas em uma, adicionando o conteúdo de more_namesa names?
Quando o .append()método é usado para essa finalidade, outra lista é criada dentro de names:
names = ["Jimmy", "Timmy"]
more_names = ["Kenny", "Lenny"]
#add contents of more_names to names
names.append(more_names)
print(names)
#output
#['Jimmy', 'Timmy', ['Kenny', 'Lenny']]
Então, .append()adiciona os novos elementos como outra lista, anexando o objeto ao final.
Para realmente concatenar (adicionar) listas e combinar todos os itens de uma lista para outra , você precisa usar o .extend()método.
A sintaxe geral fica assim:
list_name.extend(iterable/other_list_name)
Vamos decompô-lo:
list_nameé o nome de uma das listas..extend()é o método para adicionar todo o conteúdo de uma lista a outra.iterablepode ser qualquer iterável, como outra lista, por exemplo,another_list_name. Nesse caso,another_list_nameé uma lista que será concatenada comlist_name, e seu conteúdo será adicionado um a um ao final delist_name, como itens separados.
Então, tomando o exemplo anterior, quando .append()for substituído por .extend(), a saída ficará assim:
names = ["Jimmy", "Timmy"]
more_names = ["Kenny", "Lenny"]
names.extend(more_names)
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny']
Quando usamos .extend(), a nameslista foi estendida e seu comprimento aumentado em 2.
A maneira como .extend()funciona é que ele pega uma lista (ou outro iterável) como argumento, itera sobre cada elemento e, em seguida, cada elemento no iterável é adicionado à lista.
Há outra diferença entre .append()e .extend().
Quando você deseja adicionar uma string, como visto anteriormente, .append()adiciona o item inteiro e único ao final da lista:
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#add the name Dylan to the end of the list
names.append("Dylan")
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny', 'Dylan']
Se, em .extend()vez disso, você adicionasse uma string ao final de uma lista, cada caractere na string seria adicionado como um item individual à lista.
Isso ocorre porque as strings são iteráveis e .extend()iteram sobre o argumento iterável passado para ela.
Então, o exemplo acima ficaria assim:
names = ["Jimmy", "Timmy", "Kenny", "Lenny"]
#pass a string(iterable) to .extend()
names.extend("Dylan")
print(names)
#output
#['Jimmy', 'Timmy', 'Kenny', 'Lenny', 'D', 'y', 'l', 'a', 'n']
Conclusão
Resumindo, o .append()método é usado para adicionar um item ao final de uma lista existente, sem criar uma nova lista.
Quando é usado para adicionar uma lista a outra lista, cria uma lista dentro de uma lista.
Se você quiser saber mais sobre Python, confira a Certificação Python do freeCodeCamp . Você começará a aprender de maneira interativa e amigável para iniciantes. Você também construirá cinco projetos no final para colocar em prática o que aprendeu.
fonte: https://www.freecodecamp.org