How does Java compare in terms of speed to C or C++ or C# or Python? The answer depends greatly on the type of application you’re running. No benchmark is perfect, but The Computer Language Benchmarks Game is a good starting point
NB: When I say “Python”, I’m talking about the reference implementation of the language, CPython. I will refer to other runtimes in this article.
I want to answer this question: When Python completes a comparable application 2–10x slower than another language, why is it slow and can’t we make it faster?
Here are the top theories:
Which one of these reasons has the biggest impact on performance?
Modern computers come with CPU’s that have multiple cores, and sometimes multiple processors. In order to utilise all this extra processing power, the Operating System defines a low-level structure called a thread, where a process (e.g. Chrome Browser) can spawn multiple threads and have instructions for the system inside. That way if one process is particularly CPU-intensive, that load can be shared across the cores and this effectively makes most applications complete tasks faster.
My Chrome Browser, as I’m writing this article, has 44 threads open. Keep in mind that the structure and API of threading are different between POSIX-based (e.g. Mac OS and Linux) and Windows OS. The operating system also handles the scheduling of threads.
IF you haven’t done multi-threaded programming before, a concept you’ll need to quickly become familiar with locks. Unlike a single-threaded process, you need to ensure that when changing variables in memory, multiple threads don’t try and access/change the same memory address at the same time.
When CPython creates variables, it allocates the memory and then counts how many references to that variable exist, this is a concept known as reference counting. If the number of references is 0, then it frees that piece of memory from the system. This is why creating a “temporary” variable within say, the scope of a for loop, doesn’t blow up the memory consumption of your application.
The challenge then becomes when variables are shared within multiple threads, how CPython locks the reference count. There is a “global interpreter lock” that carefully controls thread execution. The interpreter can only execute one operation at a time, regardless of how many threads it has.
If you have a single-threaded, single interpreter application. It will make no difference to the speed. Removing the GIL would have no impact on the performance of your code.
If you wanted to implement concurrency within a single interpreter (Python process) by using threading, and your threads were IO intensive (e.g. Network IO or Disk IO), you would see the consequences of GIL-contention.
If you have a web-application (e.g. Django) and you’re using WSGI, then each request to your web-app is a separate Python interpreter, so there is only 1 lock per request. Because the Python interpreter is slow to start, some WSGI implementations have a “Daemon Mode” which keep Python process(es) on the go for you.
PyPy has a GIL and it is typically >3x faster than CPython.
Jython does not have a GIL because a Python thread in Jython is represented by a Java thread and benefits from the JVM memory-management system.
I hear this a lot and I find it a gross-simplification of the way CPython actually works. If at a terminal you wrote
python myscript.py then CPython would start a long sequence of reading, lexing, parsing, compiling, interpreting and executing that code.
If you’re interested in how that process works, I’ve written about it before:
An important point in that process is the creation of a
.pyc file, at the compiler stage, the bytecode sequence is written to a file inside
__pycache__/ on Python 3 or in the same directory in Python 2. This doesn’t just apply to your script, but all of the code you imported, including 3rd party modules.
So most of the time (unless you write code which you only ever run once?), Python is interpreting bytecode and executing it locally. Compare that with Java and C#.NET:
Java compiles to an “Intermediate Language” and the Java Virtual Machine reads the bytecode and just-in-time compiles it to machine code. The .NET CIL is the same, the .NET Common-Language-Runtime, CLR, uses just-in-time compilation to machine code.
So, why is Python so much slower than both Java and C# in the benchmarks if they all use a virtual machine and some sort of Bytecode? Firstly, .NET and Java are JIT-Compiled.
JIT or Just-in-time compilation requires an intermediate language to allow the code to be split into chunks (or frames). Ahead of time (AOT) compilers are designed to ensure that the CPU can understand every line in the code before any interaction takes place.
The JIT itself does not make the execution any faster, because it is still executing the same bytecode sequences. However, JIT enables optimizations to be made at runtime. A good JIT optimizer will see which parts of the application are being executed a lot, call these “hot spots”. It will then make optimizations to those bits of code, by replacing them with more efficient versions.
This means that when your application does the same thing again and again, it can be significantly faster. Also, keep in mind that Java and C# are strongly-typed languages so the optimiser can make many more assumptions about the code.
PyPy has a JIT and as mentioned in the previous section, is significantly faster than CPython. This performance benchmark article goes into more detail —
There are downsides to JITs: one of those is startup time. CPython startup time is already comparatively slow, PyPy is 2–3x slower to start than CPython. The Java Virtual Machine is notoriously slow to boot. The .NET CLR gets around this by starting at system-startup, but the developers of the CLR also develop the Operating System on which the CLR runs.
If you have a single Python process running for a long time, with code that can be optimized because it contains “hot spots”, then a JIT makes a lot of sense.
However, CPython is a general-purpose implementation. So if you were developing command-line applications using Python, having to wait for a JIT to start every time the CLI was called would be horribly slow.
CPython has to try and serve as many use cases as possible. There was the possibility of plugging a JIT into CPython but this project has largely stalled.
If you want the benefits of a JIT and you have a workload that suits it, use PyPy.
In a “Statically-Typed” language, you have to specify the type of a variable when it is declared. Those would include C, C++, Java, C#, Go.
In a dynamically-typed language, there are still the concept of types, but the type of a variable is dynamic.
a = 1 a = "foo"
In this toy-example, Python creates a second variable with the same name and a type of
str and deallocates the memory created for the first instance of
Statically-typed languages aren’t designed as such to make your life hard, they are designed that way because of the way the CPU operates. If everything eventually needs to equate to a simple binary operation, you have to convert objects and types down to a low-level data structure.
Python does this for you, you just never see it, nor do you need to care.
Not having to declare the type isn’t what makes Python slow, the design of the Python language enables you to make almost anything dynamic. You can replace the methods on objects at runtime, you can monkey-patch low-level system calls to a value declared at runtime. Almost anything is possible.
It’s this design that makes it incredibly hard to optimise Python.
To illustrate my point, I’m going to use a syscall tracing tool that works in Mac OS called Dtrace. CPython distributions do not come with DTrace builtin, so you have to recompile CPython. I’m using 3.6.6 for my demo
wget https://github.com/python/cpython/archive/v3.6.6.zip unzip v3.6.6.zip cd v3.6.6 ./configure --with-dtrace make
python.exe will have Dtrace tracers throughout the code. Paul Ross wrote an awesome Lightning Talk on Dtrace. You can download DTrace starter files for Python to measure function calls, execution time, CPU time, syscalls, all sorts of fun. e.g.
sudo dtrace -s toolkit/<tracer>.d -c ‘../cpython/python.exe script.py’
py_callflow tracer shows all the function calls in your application
So, does Python’s dynamic typing make it slow?
Python is primarily slow because of its dynamic nature and versatility. It can be used as a tool for all sorts of problems, where more optimised and faster alternatives are probably available.
There are, however, ways of optimising your Python applications by leveraging async, understanding the profiling tools, and consider using multiple-interpreters.
For applications where startup time is unimportant and the code would benefit a JIT, consider PyPy.
For parts of your code where performance is critical and you have more statically-typed variables, consider using Cython.
In this tutorial, you’ll learn all the basics of using **IDLE** to write Python programs. You'll know what Python IDLE is and how you can use it to interact with Python directly. You’ve also learned how to work with Python files and customize Python IDLE to your liking.
In this tutorial, you'll learn how to use the development environment included with your Python installation. Python IDLE is a small program that packs a big punch! You'll learn how to use Python IDLE to interact with Python directly, work with Python files, and improve your development workflow.
If you’ve recently downloaded Python onto your computer, then you may have noticed a new program on your machine called IDLE. You might be wondering, “What is this program doing on my computer? I didn’t download that!” While you may not have downloaded this program on your own, IDLE comes bundled with every Python installation. It’s there to help you get started with the language right out of the box. In this tutorial, you’ll learn how to work in Python IDLE and a few cool tricks you can use on your Python journey!
In this tutorial, you’ll learn:
Table of Contents
Every Python installation comes with an Integrated Development and Learning Environment, which you’ll see shortened to IDLE or even IDE. These are a class of applications that help you write code more efficiently. While there are many IDEs for you to choose from, Python IDLE is very bare-bones, which makes it the perfect tool for a beginning programmer.
Python IDLE comes included in Python installations on Windows and Mac. If you’re a Linux user, then you should be able to find and download Python IDLE using your package manager. Once you’ve installed it, you can then use Python IDLE as an interactive interpreter or as a file editor.
The best place to experiment with Python code is in the interactive interpreter, otherwise known as a shell. The shell is a basic Read-Eval-Print Loop (REPL). It reads a Python statement, evaluates the result of that statement, and then prints the result on the screen. Then, it loops back to read the next statement.
The Python shell is an excellent place to experiment with small code snippets. You can access it through the terminal or command line app on your machine. You can simplify your workflow with Python IDLE, which will immediately start a Python shell when you open it.
Every programmer needs to be able to edit and save text files. Python programs are files with the
.py extension that contain lines of Python code. Python IDLE gives you the ability to create and edit these files with ease.
Python IDLE also provides several useful features that you’ll see in professional IDEs, like basic syntax highlighting, code completion, and auto-indentation. Professional IDEs are more robust pieces of software and they have a steep learning curve. If you’re just beginning your Python programming journey, then Python IDLE is a great alternative!How to Use the Python IDLE Shell
The shell is the default mode of operation for Python IDLE. When you click on the icon to open the program, the shell is the first thing that you see:
This is a blank Python interpreter window. You can use it to start interacting with Python immediately. You can test it out with a short line of code:
Here, you used
print() to output the string
"Hello, from IDLE!" to your screen. This is the most basic way to interact with Python IDLE. You type in commands one at a time and Python responds with the result of each command.
Next, take a look at the menu bar. You’ll see a few options for using the shell:
You can restart the shell from this menu. If you select that option, then you’ll clear the state of the shell. It will act as though you’ve started a fresh instance of Python IDLE. The shell will forget about everything from its previous state:
In the image above, you first declare a variable,
x = 5. When you call
print(x), the shell shows the correct output, which is the number
5. However, when you restart the shell and try to call
print(x) again, you can see that the shell prints a traceback. This is an error message that says the variable
x is not defined. The shell has forgotten about everything that came before it was restarted.
You can also interrupt the execution of the shell from this menu. This will stop any program or statement that’s running in the shell at the time of interruption. Take a look at what happens when you send a keyboard interrupt to the shell:
KeyboardInterrupt error message is displayed in red text at the bottom of your window. The program received the interrupt and has stopped executing.
Python IDLE offers a full-fledged file editor, which gives you the ability to write and execute Python programs from within this program. The built-in file editor also includes several features, like code completion and automatic indentation, that will speed up your coding workflow. First, let’s take a look at how to write and execute programs in Python IDLE.
To start a new Python file, select File → New File from the menu bar. This will open a blank file in the editor, like this:
From this window, you can write a brand new Python file. You can also open an existing Python file by selecting File → Open… in the menu bar. This will bring up your operating system’s file browser. Then, you can find the Python file you want to open.
If you’re interested in reading the source code for a Python module, then you can select File → Path Browser. This will let you view the modules that Python IDLE can see. When you double click on one, the file editor will open up and you’ll be able to read it.
The content of this window will be the same as the paths that are returned when you call
sys.path. If you know the name of a specific module you want to view, then you can select File → Module Browser and type in the name of the module in the box that appears.
Once you’ve opened a file in Python IDLE, you can then make changes to it. When you’re ready to edit a file, you’ll see something like this:
The contents of your file are displayed in the open window. The bar along the top of the window contains three pieces of important information:
In the image above, you’re editing the file
myFile.py, which is located in the
Documents folder. The Python version is 3.7.1, which you can see in parentheses.
There are also two numbers in the bottom right corner of the window:
It’s useful to see these numbers so that you can find errors more quickly. They also help you make sure that you’re staying within a certain line width.
There are a few visual cues in this window that will help you remember to save your work. If you look closely, then you’ll see that Python IDLE uses asterisks to let you know that your file has unsaved changes:
The file name shown in the top of the IDLE window is surrounded by asterisks. This means that there are unsaved changes in your editor. You can save these changes with your system’s standard keyboard shortcut, or you can select File → Save from the menu bar. Make sure that you save your file with the
.py extension so that syntax highlighting will be enabled.
When you want to execute a file that you’ve created in IDLE, you should first make sure that it’s saved. Remember, you can see if your file is properly saved by looking for asterisks around the filename at the top of the file editor window. Don’t worry if you forget, though! Python IDLE will remind you to save whenever you attempt to execute an unsaved file.
To execute a file in IDLE, simply press the F5 key on your keyboard. You can also select Run → Run Module from the menu bar. Either option will restart the Python interpreter and then run the code that you’ve written with a fresh interpreter. The process is the same as when you run
python3 -i [filename] in your terminal.
When your code is done executing, the interpreter will know everything about your code, including any global variables, functions, and classes. This makes Python IDLE a great place to inspect your data if something goes wrong. If you ever need to interrupt the execution of your program, then you can press Ctrl+C in the interpreter that’s running your code.How to Improve Your Workflow
Now that you’ve seen how to write, edit, and execute files in Python IDLE, it’s time to speed up your workflow! The Python IDLE editor offers a few features that you’ll see in most professional IDEs to help you code faster. These features include automatic indentation, code completion and call tips, and code context.
IDLE will automatically indent your code when it needs to start a new block. This usually happens after you type a colon (
:). When you hit the enter key after the colon, your cursor will automatically move over a certain number of spaces and begin a new code block.
You can configure how many spaces the cursor will move in the settings, but the default is the standard four spaces. The developers of Python agreed on a standard style for well-written Python code, and this includes rules on indentation, whitespace, and more. This standard style was formalized and is now known as PEP 8. To learn more about it, check out How to Write Beautiful Python Code With PEP 8.
When you’re writing code for a large project or a complicated problem, you can spend a lot of time just typing out all of the code you need. Code completion helps you save typing time by trying to finish your code for you. Python IDLE has basic code completion functionality. It can only autocomplete the names of functions and classes. To use autocompletion in the editor, just press the tab key after a sequence of text.
Python IDLE will also provide call tips. A call tip is like a hint for a certain part of your code to help you remember what that element needs. After you type the left parenthesis to begin a function call, a call tip will appear if you don’t type anything for a few seconds. For example, if you can’t quite remember how to append to a list, then you can pause after the opening parenthesis to bring up the call tip:
The call tip will display as a popup note, reminding you how to append to a list. Call tips like these provide useful information as you’re writing code.
The code context functionality is a neat feature of the Python IDLE file editor. It will show you the scope of a function, class, loop, or other construct. This is particularly useful when you’re scrolling through a lengthy file and need to keep track of where you are while reviewing code in the editor.
To turn it on, select Options → Code Context in the menu bar. You’ll see a gray bar appear at the top of the editor window:
As you scroll down through your code, the context that contains each line of code will stay inside of this gray bar. This means that the
print() functions you see in the image above are a part of a main function. When you reach a line that’s outside the scope of this function, the bar will disappear.
A bug is an unexpected problem in your program. They can appear in many forms, and some are more difficult to fix than others. Some bugs are tricky enough that you won’t be able to catch them by just reading through your program. Luckily, Python IDLE provides some basic tools that will help you debug your programs with ease!
If you want to run your code with the built-in debugger, then you’ll need to turn this feature on. To do so, select Debug → Debugger from the Python IDLE menu bar. In the interpreter, you should see
[DEBUG ON] appear just before the prompt (
>>>), which means the interpreter is ready and waiting.
When you execute your Python file, the debugger window will appear:
In this window, you can inspect the values of your local and global variables as your code executes. This gives you insight into how your data is being manipulated as your code runs.
You can also click the following buttons to move through your code:
Be careful, because there is no reverse button! You can only step forward in time through your program’s execution.
You’ll also see four checkboxes in the debug window:
When you select one of these, you’ll see the relevant information in your debug window.
A breakpoint is a line of code that you’ve identified as a place where the interpreter should pause while running your code. They will only work when DEBUG mode is turned on, so make sure that you’ve done that first.
To set a breakpoint, right-click on the line of code that you wish to pause. This will highlight the line of code in yellow as a visual indication of a set breakpoint. You can set as many breakpoints in your code as you like. To undo a breakpoint, right-click the same line again and select Clear Breakpoint.
Once you’ve set your breakpoints and turned on DEBUG mode, you can run your code as you would normally. The debugger window will pop up, and you can start stepping through your code manually.
When you see an error reported to you in the interpreter, Python IDLE lets you jump right to the offending file or line from the menu bar. All you have to do is highlight the reported line number or file name with your cursor and select Debug → Go to file/line from the menu bar. This is will open up the offending file and take you to the line that contains the error. This feature works regardless of whether or not DEBUG mode is turned on.
Python IDLE also provides a tool called a stack viewer. You can access it under the Debug option in the menu bar. This tool will show you the traceback of an error as it appears on the stack of the last error or exception that Python IDLE encountered while running your code. When an unexpected or interesting error occurs, you might find it helpful to take a look at the stack. Otherwise, this feature can be difficult to parse and likely won’t be useful to you unless you’re writing very complicated code.How to Customize Python IDLE
There are many ways that you can give Python IDLE a visual style that suits you. The default look and feel is based on the colors in the Python logo. If you don’t like how anything looks, then you can almost always change it.
To access the customization window, select Options → Configure IDLE from the menu bar. To preview the result of a change you want to make, press Apply. When you’re done customizing Python IDLE, press OK to save all of your changes. If you don’t want to save your changes, then simply press Cancel.
There are 5 areas of Python IDLE that you can customize:
Let’s take a look at each of them now.
The first tab allows you to change things like font color, font size, and font style. You can change the font to almost any style you like, depending on what’s available for your operating system. The font settings window looks like this:
You can use the scrolling window to select which font you prefer. (I recommend you select a fixed-width font like Courier New.) Pick a font size that’s large enough for you to see well. You can also click the checkbox next to Bold to toggle whether or not all text appears in bold.
This window will also let you change how many spaces are used for each indentation level. By default, this will be set to the PEP 8 standard of four spaces. You can change this to make the width of your code more or less spread out to your liking.
The second customization tab will let you change highlights. Syntax highlighting is an important feature of any IDE that highlights the syntax of the language that you’re working in. This helps you visually distinguish between the different Python constructs and the data used in your code.
Python IDLE allows you to fully customize the appearance of your Python code. It comes pre-installed with three different highlight themes:
You can select from these pre-installed themes or create your own custom theme right in this window:
Unfortunately, IDLE does not allow you to install custom themes from a file. You have to create customs theme from this window. To do so, you can simply start changing the colors for different items. Select an item, and then press Choose color for. You’ll be brought to a color picker, where you can select the exact color that you want to use.
You’ll then be prompted to save this theme as a new custom theme, and you can enter a name of your choosing. You can then continue changing the colors of different items if you’d like. Remember to press Apply to see your changes in action!
The third customization tab lets you map different key presses to actions, also known as keyboard shortcuts. These are a vital component of your productivity whenever you use an IDE. You can either come up with your own keyboard shortcuts, or you can use the ones that come with IDLE. The pre-installed shortcuts are a good place to start:
The keyboard shortcuts are listed in alphabetical order by action. They’re listed in the format Action - Shortcut, where Action is what will happen when you press the key combination in Shortcut. If you want to use a built-in key set, then select a mapping that matches your operating system. Pay close attention to the different keys and make sure your keyboard has them!
The customization of the keyboard shortcuts is very similar to the customization of syntax highlighting colors. Unfortunately, IDLE does not allow you to install custom keyboard shortcuts from a file. You must create a custom set of shortcuts from the Keys tab.
Select one pair from the list and press Get New Keys for Selection. A new window will pop up:
Here, you can use the checkboxes and scrolling menu to select the combination of keys that you want to use for this shortcut. You can select Advanced Key Binding Entry >> to manually type in a command. Note that this cannot pick up the keys you press. You have to literally type in the command as you see it displayed to you in the list of shortcuts.
The fourth tab of the customization window is a place for small, general changes. The general settings tab looks like this:
Here, you can customize things like the window size and whether the shell or the file editor opens first when you start Python IDLE. Most of the things in this window are not that exciting to change, so you probably won’t need to fiddle with them much.
The fifth tab of the customization window lets you add extensions to Python IDLE. Extensions allow you to add new, awesome features to the editor and the interpreter window. You can download them from the internet and install them to right into Python IDLE.
To view what extensions are installed, select Options → Configure IDLE -> Extensions. There are many extensions available on the internet for you to read more about. Find the ones you like and add them to Python IDLE!Conclusion
In this tutorial, you’ve learned all the basics of using IDLE to write Python programs. You know what Python IDLE is and how you can use it to interact with Python directly. You’ve also learned how to work with Python files and customize Python IDLE to your liking.
You’ve learned how to:
Now you’re armed with a new tool that will let you productively write Pythonic code and save you countless hours down the road. Happy programming!
Python is one among the most easiest and user friendly programming languages when it comes to the field of software engineering. The codes and syntaxes of python is so simple and easy to use that it can be deployed in any problem solving...
Python is one among the most easiest and user friendly programming languages when it comes to the field of software engineering. The codes and syntaxes of python is so simple and easy to use that it can be deployed in any problem solving challenges. The codes of Python can easily be deployed in Data Science and Machine Learning. Due to this ease of deployment and easier syntaxes, this platform has a lot of real world problem solving applications. According to the sources the companies are eagerly hunting for the professionals with python skills along with SQL. An average python developer in the united states makes around 1 lakh U.S Dollars per annum. In some of the top IT hubs in our country like Bangalore, the demand for professionals in the domains of Data Science and Python Programming has surpassed over the past few years. As a result of which a lot of various python certification courses are available right now.
Array in Python: An array is defined as a data structure that can hold a fixed number of elements that are of the same python data type. The following are some of the basic functions of array in python:
Along with this one can easily crack any python interview by means of python interview questions
This video on Tkinter tutorial covers all the basic aspects of creating and making use of your own simple Graphical User Interface (GUI) using Python. It establishes all of the concepts needed to get started with building your own user interfaces while coding in Python.
This video on Tkinter tutorial covers all the basic aspects of creating and making use of your own simple Graphical User Interface (GUI) using Python. It establishes all of the concepts needed to get started with building your own user interfaces while coding in Python.
Original video source: https://www.youtube.com/watch?v=VMP1oQOxfM0