Adam Daniels

Adam Daniels

1567999177

A guide to Python Closures

Originally published at https://www.geeksforgeeks.org

Before seeing what a closure is, we have to first understand what are nested functions and non-local variables.

Nested functions in Python

A function which is defined inside another function is known as nested function. Nested functions are able to access variables of the enclosing scope.

In Python, these non-local variables can be accessed only within their scope and not outside their scope. This can be illustrated by following example:

# Python program to illustrate 
# nested functions 
def outerFunction(text): 
	text = text 
def innerFunction(): 
	print(text) 


innerFunction() 

if name == ‘main’: 
outerFunction(‘Hey!’) 

As we can see innerFunction() can easily be accessed inside the outerFunction body but not outside of it’s body. Hence, here, innerFunction() is treated as nested Function which uses text as non-local variable.

Python Closures

A Closure is a function object that remembers values in enclosing scopes even if they are not present in memory.

  • It is a record that stores a function together with an environment: a mapping associating each free variable of the function (variables that are used locally, but defined in an enclosing scope) with the value or reference to which the name was bound when the closure was created.
  • A closure—unlike a plain function—allows the function to access those captured variables through the closure’s copies of their values or references, even when the function is invoked outside their scope.
# Python program to illustrate 

closures 

def outerFunction(text): 
text = text 

def innerFunction(): 
	print(text) 


return innerFunction # Note we are returning function WITHOUT parenthesis 

if name == ‘main’: 
myFunction = outerFunction(‘Hey!’) 
myFunction() 


Output:
omkarpathak@omkarpathak-Inspiron-3542:
~/Documents/Python-Programs/$ python Closures.py
Hey!
  1.  As observed from above code, closures help to invoke function outside their scope.
  2. The function innerFunction has its scope only inside the outerFunction. But with the use of closures we can easily extend its scope to invoke a function outside its scope.
# Python program to illustrate 

closures 

import logging 
logging.basicConfig(filename=‘example.log’, level=logging.INFO

def logger(func): 
def log_func(*args): 
logging.info
‘Running “{}” with arguments {}’.format(func.name, args)) 
print(func(*args)) 
# Necessary for closure to work (returning WITHOUT parenthesis) 
return log_func  

def add(x, y): 
return x+y 

def sub(x, y): 
return x-y 

add_logger = logger(add) 
sub_logger = logger(sub) 

add_logger(3, 3) 
add_logger(4, 5) 

sub_logger(10, 5) 
sub_logger(20, 10) 


OUTPUT:
omkarpathak@omkarpathak-Inspiron-3542:
~/Documents/Python-Programs/$ python MoreOnClosures.py
6
9
5
10

When and why to use Closures:

  1. As closures are used as callback functions, they provide some sort of data hiding. This helps us to reduce the use of global variables.
  2. When we have few functions in our code, closures prove to be efficient way. But if we need to have many functions, then go for class (OOP). 

Thanks for reading

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Further reading

Python Tutorial - Python GUI Programming - Python GUI Examples (Tkinter Tutorial)

Python Tutorial: Image processing with Python (Using OpenCV)

An A-Z of useful Python tricks


#python #function

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Buddha Community

A guide to Python Closures
Ray  Patel

Ray Patel

1619518440

top 30 Python Tips and Tricks for Beginners

Welcome to my Blog , In this article, you are going to learn the top 10 python tips and tricks.

1) swap two numbers.

2) Reversing a string in Python.

3) Create a single string from all the elements in list.

4) Chaining Of Comparison Operators.

5) Print The File Path Of Imported Modules.

6) Return Multiple Values From Functions.

7) Find The Most Frequent Value In A List.

8) Check The Memory Usage Of An Object.

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Ray  Patel

Ray Patel

1619510796

Lambda, Map, Filter functions in python

Welcome to my Blog, In this article, we will learn python lambda function, Map function, and filter function.

Lambda function in python: Lambda is a one line anonymous function and lambda takes any number of arguments but can only have one expression and python lambda syntax is

Syntax: x = lambda arguments : expression

Now i will show you some python lambda function examples:

#python #anonymous function python #filter function in python #lambda #lambda python 3 #map python #python filter #python filter lambda #python lambda #python lambda examples #python map

Art  Lind

Art Lind

1602968400

Python Tricks Every Developer Should Know

Python is awesome, it’s one of the easiest languages with simple and intuitive syntax but wait, have you ever thought that there might ways to write your python code simpler?

In this tutorial, you’re going to learn a variety of Python tricks that you can use to write your Python code in a more readable and efficient way like a pro.

Let’s get started

Swapping value in Python

Instead of creating a temporary variable to hold the value of the one while swapping, you can do this instead

>>> FirstName = "kalebu"
>>> LastName = "Jordan"
>>> FirstName, LastName = LastName, FirstName 
>>> print(FirstName, LastName)
('Jordan', 'kalebu')

#python #python-programming #python3 #python-tutorials #learn-python #python-tips #python-skills #python-development

Art  Lind

Art Lind

1602666000

How to Remove all Duplicate Files on your Drive via Python

Today you’re going to learn how to use Python programming in a way that can ultimately save a lot of space on your drive by removing all the duplicates.

Intro

In many situations you may find yourself having duplicates files on your disk and but when it comes to tracking and checking them manually it can tedious.

Heres a solution

Instead of tracking throughout your disk to see if there is a duplicate, you can automate the process using coding, by writing a program to recursively track through the disk and remove all the found duplicates and that’s what this article is about.

But How do we do it?

If we were to read the whole file and then compare it to the rest of the files recursively through the given directory it will take a very long time, then how do we do it?

The answer is hashing, with hashing can generate a given string of letters and numbers which act as the identity of a given file and if we find any other file with the same identity we gonna delete it.

There’s a variety of hashing algorithms out there such as

  • md5
  • sha1
  • sha224, sha256, sha384 and sha512

#python-programming #python-tutorials #learn-python #python-project #python3 #python #python-skills #python-tips

Biju Augustian

Biju Augustian

1574340419

Guide to Python Programming Language

Description
The course will lead you from beginning level to advance in Python Programming Language. You do not need any prior knowledge on Python or any programming language or even programming to join the course and become an expert on the topic.

The course is begin continuously developing by adding lectures regularly.

Please see the Promo and free sample video to get to know more.

Hope you will enjoy it.

Basic knowledge
An Enthusiast Mind
A Computer
Basic Knowledge To Use Computer
Internet Connection
What will you learn
Will Be Expert On Python Programming Language
Build Application On Python Programming Language

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