Python REPL 

REPL is an acronym for Read, Evaluate, Print, and Loop. Developers use REPL Python to communicate with the Python Interpreter.  

In contrast to running a Python file, you can input commands in the REPL and see the results displayed immediately. The Python REPL also lets you print out object and method help, a list of all the accessible methods, and much more.

What is Python REPL?

Python REPL is used by coders and developers to communicate with the computer in Python. 

What Does REPL in Python Mean? 

Python offers an interactive REPL that you can use to communicate with your computer. The computer does these four tasks to make it work:

  • Read your Python commands.
  • Evaluate your code to work out what the input means.
  • Print the results to see the computer’s response.
  • Loop back to step 1 to keep communicating.

The computer displays three chevrons (>>>) or a numbered message (In [1]:) to let you know it is awaiting instructions. Simply enter your commands, then press Return to have the computer process them.

The REPL is used by programmers to work things out.  Similar to a journal, you can “rough out” ideas and investigate problems using it. A REPL’s immediate input makes it simple to improvise, explore, and learn more about what the computer is doing. This is one of Mu’s most helpful features, and after you get used to the REPL, you’ll wonder how you ever got along without it.

Even though all REPLs operate in the same way, the features and functionalities of the REPL will differ based on the mode you’re currently using in Mu. However, two extremely helpful commands will operate on all REPL versions: help and dir.

The dir command informs you of what is present. It will inform you of what Python currently understands if you use it on its own:

>>> dir()
['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__',
'__package__', '__spec__']

Best Python REPL 

PTP Python is considered to be the better or even the best Python REPL with Autocompletion, Autosuggestion, Docstring, and History Insertion. 

To set up and install PTP Python, type:

pip install ptpython

Then, type:

Ptpython

To begin using the language.

On a standard Python shell, if you make a mistake and press Enter, you cannot go back and fix it. Fortunately, ptpython lets you validate the input before pressing the Enter key.

Have you ever wanted to get a suggestion based on history? Ptpython can be used to accomplish that.

This function is disabled by default. However, you can activate it simply by using F2 to open the menu. The “Auto suggestion” option can then be activated by using the right or left arrows. Press Enter to close the menu.

When you exit the ptpython shell, all modifications you made to its settings will be undone.

Copy this file to $XDG CONFIG HOME/ptpython/config.py to make a permanent update to the configuration. The same will be /.config/ptpython/config.py on a Linux system.

You should have all the features activated after copying the configuration file to your local directory. You are allowed to modify the configuration files to match your preferences.

How to Use Python REPLs

Open the command palette, look for “Start REPL,” and then select it to launch the REPL in VS Code. Starting the REPL from within VS Code has the benefit of respecting the environment you’ve already configured, specifically the version of Python you selected earlier.

Note: Type python in your shell to launch the REPL from the command line outside of the editor.

When you run this command, a new pane should appear at the bottom of your editor where you can type. It’s a fantastic feature of the REPL, where we can see the outcomes of commands right away.

Let’s become acquainted with the REPL.

  • Comments always begin with a #. 
  •  >>> – This is the prompt. In the example code, lines beginning with >>> denote input lines. Without either of these lines, the output is produced by executing the input from the prompt. 
  • Type >>> at the prompt, and then press Enter after each line to execute them.

Example:

# My REPL. Don't copy the >>> symbols. That means the code was entered
# into the prompt.
#
# If the line does not start with >>>, that means it is output,
# not input
>>> name = "Hina"
>>> name
'Hina'

Any variable can be entered into the prompt to display its value in the REPL.

Code, even numerous lines of it, can be copied and pasted into the REPL at once. 

When you copy the three lines below and paste them into your REPL, what is the outcome?

Input:

x = 5 
y = 33.5
x * y

Output:  

>>> x = 5

>>> y = 33.5

>>> x * y

167.5

The REPL is a fantastic learning tool as it enables us to gather data about our Python program in real time.

For dealing with the MicroPython REPL, there are some helpful shortcuts.  Use these key combinations for a shortcut:

  • Enter raw REPL mode by pressing Ctrl-A on a blank line. The only difference between this and permanent paste mode is that characters are not echoed back.
  • On a blank line, pressing Ctrl-B enters REPL mode as usual.
  • Any input is cancelled by pressing Ctrl-C, and the active program is also interrupted.
  • Ctrl-D will do a soft reset on a blank line.
  • You can copy and paste sections of text by pressing Ctrl-E, which activates the “paste mode.” Ctrl-D can be used to exit this mode.
  • Ctrl-F causes the device to “safe-boot,” which stops boot.py and main.py from running.

Conclusion

Python REPL is a good tool for both beginners and skilled programmers. It offers a computer environment where you can read and evaluate the inputs and get immediate results. REPLs give an interactive environment to explore different tools in different programming languages. The Python REPL enables you to communicate with the precise state that your application runtime is in.

FAQs

  • Is REPL a Good Option for Developers?

Yes, whether a novice or an expert Python developer, using REPL is a good choice for developers.

  • Is REPL a Programming Language?

REPL is not a programming language. Instead, it’s an environment which takes the input from the user, evaluates it and then produces the output.

Learn coding basics for free

Don’t let the information above phase you. If you’ve landed on this page, it’s a good start. If you’re new to software development and want to learn some basic programming, register for our free 5 Day Coding Challenge through the form below. If you’ve already done the coding challenge, we do teach Python as part of our Full Stack Software Development Programme. Click here to find out more. Alternatively, if you want to try some Python, check out our Python cheat sheet.

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