Python Statement, Indentation and Comments

Updated: Aug 21, 2020



Python Statement, Indentation and Comments



In this tutorial, you will learn about Python statements, why indentation is important, and the use of comments in programming.


Python Statement


Instructions that a Python interpreter can execute are called statements. For example, a = 7 is an assignment statement. if statement, for statement, while statement, etc. are other kinds of statements which will be discussed later.


Single line statement

Example:


a=7


Multi-line statement


In Python, the end of a statement is marked by a newline character. But we can make a statement extend over multiple lines with the line continuation character (\).

Example:

 
 a = 1 + 2 + 3 + \
  4 + 5 + 6 + \
  7 + 8 + 9
 

This is an explicit line continuation. In Python, line continuation is implied inside parentheses ( ), brackets [ ], and braces { }. For instance, we can implement the above multi-line statement as:

Example:

 
 a = (1 + 2 + 3 +
  4 + 5 + 6 +
  7 + 8 + 9)
 

Here, the surrounding parentheses ( ) do the line continuation implicitly. Same is the case with [ ] and { }.

Example:

 
 colors = ['red',
  'blue',
  'green']
 

We can also put multiple statements in a single line using semicolons, as follows:

Example:


 a = ‘Welcome’; b = ‘to’; c = ‘Linux Advise’
 

Blank Lines Python Statements


The interpreter simply ignores blank lines.


Python Indentation


Most of the programming languages like C, C++, and Java use braces { } to define a block of code. Python, however, uses indentation.


A code block (body of a function, loop, etc.) starts with indentation and ends with the first non-indented line. The amount of indentation is up to you, but it must be consistent throughout that block.


Generally, four white spaces are used for indentation and are preferred over tabs.

Example:


for i in range(1,10):
  print(i)
  if i == 7:
     break
  

Output:


1
2
3
4
5
6
7



The enforcement of indentation in Python makes the code look neat and clean. This results in Python programs that look similar and consistent.

Indentation can be ignored in line continuation, but it's always a good idea to indent. It makes the code more readable.

Example:


if True:
 print('Linuxadvise')
 a = 10 
 

and

 
 if True: print('Linuxadvise'); a = 10
 

Output:


  Linuxadvise

both are valid and do the same thing, but the former style is clearer.

Incorrect indentation will result in IndentationError.

Python Comments


Comments are very important while writing a program. They describe what is going on inside a program so that a person looking at the source code does not have a hard time figuring it out.


  • You might forget the key details of the program you just wrote in a month's time. So taking the time to explain these concepts in the form of comments is always fruitful.

  • In Python, we use the hash (#) symbol to start writing a comment.

  • It extends up to the newline character. Comments are for programmers to better understand a program.

  • Python Interpreter ignores comments.

Example:


#This is a one line comment
#print out Linuxadvise
print(' Linuxadvise')

Output:


  Linuxadvise


Multi-line comments


We can have comments that extend up to multiple lines. One way is to use the hash(#) symbol at the beginning of each line.

Example:

 
 #This is a long comment
 #and it extends
 #to multiple lines
 

Another way of doing this is to use triple quotes, either ''' or """.

These triple quotes are generally used for multi-line strings. But they can be used as a multi-line comment as well. Unless they are not docstrings, they do not generate any extra code.

Example:

 
 """This is also a
 perfect example of
 multi-line comments"""
 

Docstrings in Python


A docstring is short for documentation string.

Python docstrings (documentation strings) are the string literals that appear right after the definition of a function, method, class, or module.


Triple quotes are used while writing docstrings. For example:

 
 def double(num):
   """ This Function to multiple by 3 the value """
   return 3*num
 

Docstrings appear right after the definition of a function, class, or module. This separates docstrings from multi-line comments using triple quotes.


The docstrings are associated with the object as their __doc__ attribute.

So, we can access the docstrings of the above function with the following lines of code:

Example:


def double(num):
  """This Function to multiple by 3 the value"""
  return 3*num
print(double.__doc__)

Output:


 
 This Function to multiple by 3 the value
 


Alright coders let's move to Comparison Operators.












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