Python Comments: Single and Multi-line

In this post you will learn about comments in python and how to write single-line and multi-line comments in python.

What are comments?

Comments are texts that are ignored by the python interpreter and never going to execute.They are written so that programmers can understand what a particular line or block of code is doing.In below sections,we will see how we can write comments in python.

Single line comment

Single line comments are preceded by a “#” symbol.You can write single line comments before starting of code,or you can write single line comments after the code on the same line,like shown below.

#This is a comments
print("Single line comment")

print("Hello") #Comment on same line

Multi-line comments in python

Python does not supports multi-line comments directly.But,we can use some hacks to add multi-line comments in python.Below I have mentioned 2 ways in which you can add multi-line comments in python.

1: Repeated Single Line comment

This is the real and recommended way of adding multi-line comments in python by PEP8 style guide. You write multiple single line comments before the code like below.

#This is a 
#multiline
#comments
print("Multiline comment")

Now,you must be thinking that,this is very time consuming and irritating because you have to write “#” in front of every line to make it a comment.One thing you can do is,you can use multi-line editing features of various editors like sublime text,atom,notepad++ etc,to edit multiple lines at the same time.

2: Multi-line strings

We can use multi-line string that are enclosed withing triple inverted commas ( “””—–“””) as a comments. Now, this is the hack which we are using to add a multi-line comments in our code. But,this is not a true comments. This is like,adding a string to our code without assigning it to a variable and never using that string in our code.

"""This is a 
way of 
adding multi-lne
comment"""

"""This is a 
way of 
adding multi-lne
comment

"""

    """this multiline
comment will give error"""

In above example,I have written 3 multi-line comments.First and Second one will not give any error.Third one will give a Indentation error,because starting “”” of the Third comment is indented,so that’s why we need to always use proper indentation for the starting “”” of the multi-line comments. For the ending “””, we don’t have any restriction on indentation,we can write it anywhere on the same line or on the next line of comments.

3: Multi-line string comment in functions and classes

We can use multi-line string comments in functions and classes too.But,one thing we need to remember is that,whenever multi-line string is written directly after the function signature or class signature,then it’s not treated as a comments,in that case it’s treated as a docstring.

def square(num): #Function signature
    """This will
       become docdring
       as it is after
       the function signature"""
    print(num*num)


def cube(num): #Function signature
    print(num*num*num)

    """This will
       become a multiline string
       commnets as it is not after
       the function signature"""
   

Now,lets see what __doc__ prints for both of these functions.We can print docstring of these functions using print (function_name.__doc). After printing docstring for above two function,the output is

Docstring for Square:

This will
       become docdring
       as it is after
       the function signature

Docstring for Cube:

None

As you can see from output,doctring for Cube function prints nothing because the multi-line comment was not after the function signature.But in square function,as multi-line comment was after the function signature,it turned into function docstring instead of multi-line comment.

So,that all for this tutorial.I hope,I explained everything about Python’s single-line and Multi-line comments in a way.if you have any doubt or any suggestion,feel free to comment down below.

Thank You.

Amarjeet

About Amarjeet

Amarjeet,BE in CS ,love to code in python and passionate about Machine Learning and Data Science. Expertsteaching.com is just a medium to share what I have learned till now with world.
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