Statements, Comments, DocString and Indentation in Python

In this Python article, we will learn about indentation, statements, comments and will also implement some examples.

1. Comments

When we want to put a note or description in our code so that other people can understand the code, we use Comments. Comments are pieces of code that the compiler ignores or simply does not execute.

Note: As a good coding practice we should try to write the code in a way that the code is self-explanatory and we do not need comments to explain our code. But sometimes the situations are tricky and we should add comments such that it compliments the code.

Let’s discuss and implement the two ways to insert comments in a python program.

1.1. Single line comments

The comments that begin with # are single-line comments and the compiler will not execute anything written after # in that specific line.

Let’s use single line comments in a python program.

#In this program, we are printing a quote
print("It's a beautiful day to save lives")

Output
It's a beautiful day to save lives

So the example above, the compiler ignored the first line which we used to keep a note of what does this program does.

But if you want to write a comment of more than a line example about the date of creation, author, description etc. For this, we have a multi-line comment in python.

1.2. Multi-line comment

If we want to write multiple lines of comments then we can simply use # multiple times, right?

# Date-of-creation : 27-01-2021
# Author: Codingeek
# Description: In this program, we are printing a quote
print("It's a beautiful day to save lives")

Output
It's a beautiful day to save lives

Comments are used to make code more readable and this doesn’t look good, and we have to use # every time we are writing a new comment.

But no issue, python has a solution for it that is easier than the above method. So, to create a multi-line comment in python we need to mark the beginning and end of the comments with either three double quotes(""") or three single quotes(''').

"""Date-of-creation : 27-01-2021
    Author: Codingeek
    Description: In this program, we are printing a quote"""
print("It's a beautiful day to save lives")

'''Date-of-creation : 27-01-2021
    Author: Codingeek
    Description: In this program, we are printing a quote'''
print("It's a beautiful day to save lives")

Both the programs above will generate the same output, we just have used two different methods to write multi-line comments.

Output
It's a beautiful day to save lives

1.3. Docstring

Docstring is written the same way as we write multi-line comments using either three double quotes(""") or three single quotes(''').

Docstring is used for the official documentation of our code. This documentation can later be used to generate guides and documentation in different formats like HTML, pdf, etc.

We can use docstring in the class, function, method, etc. It should be the first statement in the object’s definition so that the other developer or consumers of that code, library, API can understand the code and meaning of parameters if any.

Let’s understand docstring using an example:

def quote():
    '''
   This function prints a quote.
    '''
    print("It's a beautiful day to save lives.")

print("the docstring value..")
print(quote.__doc__)

Output:-
the docstring value...

   This function prints a quote.

REMEMBER : Python docstrings are not comments

You can check the docstring of any object in python using __doc__

Python 3.9.1 (tags/v3.9.1:1e5d33e, Dec  7 2020, 17:08:21) [MSC v.1927 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license()" for more information.
>>> sum.__doc__
"Return the sum of a 'start' value (default: 0) plus an iterable of numbers\n\nWhen the iterable is empty, return the start value.\nThis function is intended specifically for use with numeric values and may\nreject non-numeric types."

2. Difference between Docstring and Comments

Let’s discuss how docstring is different from comments in Python.

3. Statements

Statements are the instructions given to a computer to perform different tasks be it data modifications, making decisions, or repeating actions. There are different types of statement in Python

a = 1            #assignment statement
for  i in range(10):            #compound statement
             pass

Compound statements are a group of statements in a block and we can achieve it by indentation. if statement, while statement, for statement, try statement, with statement, function definition, class definition are some of the examples of compound statements.

• Multiple statement in a single line using ;

a =1 ; print("Hello"); print("HI")

Output
Hello
HI

• Breaking a single statement into multiple lines

print("It's a \
beautiful day \
to save \
lives ")

Output
It's a beautiful day to save lives

How does the compiler know that this is a whole block or it’s a compound statement? So for this, we talk of a concept called Indentation.

4. Indentation

Indentation is basically white spaces before the statements which help the compiler to understand the python program. For writing compound statements, every statement should have the same no. of white spaces or tabs before the statements.

def quote():
    print("Quote by Derek Shepard-")
    print("It's a beautiful day to save lives.")

quote()

Output
Quote by Derek Shepard-
It's a beautiful day to save lives

In the above example, the python compiler knew the function definition has ended because of the indentation. If the indentation is miswritten, the compiler will give an error known as Indentation error.

def quote():
    print("Quote by Derek Shepard")
print("--------------")
    print("It's a beautiful day to save lives.")

quote()

Output
  File "c:\Users\parih\Desktop\Kaggle\anime-Task-1\testing.py", line 4
    print("It's a beautiful day to save lives.")
IndentationError: unexpected indent

5. Conclusion

In this article, we discussed single line and multi-line comments, what is a docstring, and how it is different from comments, different types of statements, Python indentation, and Indentation error.

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Complete code samples are present on Github project.

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