Lesson 03 python statement, indentation and comments

Lesson 03

Python Statement, Indentation
and Comments
Perth AI School

Python Statement, Indentation and Comments
Python Statement
Instructions that a Python interpreter can execute are called statements. For example, is
an assignment statement. statement, statement, statement, etc. are other kinds of
statements which will be discussed later.
a = 1
if for while
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 (). For 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:
( ) [ ] { }
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 . For example:
( )
[ ] { }
colors = [ ,
,
]
'red'
'blue'
'green'
We can also put multiple statements in a single line using semicolons, as follows:
a = ; b = ; c =1 2 3

Python Indentation
Most of the programming languages like C, C++, and Java use braces to de ne a block of
code. Python, however, uses indentation.
{ }
: ( ); a =if True print 'Hello' 5
A code block (body of a function, loop, etc.) starts with indentation and ends with the rst
unindented line. The amount of indentation is up to you, but it must be consistent
throughout that block.
both are valid and do the same thing, but the former style is clearer.
Generally, four whitespaces are used for indentation and are preferred over tabs. Here is an
example.
i range( , ):
(i)
i == :
for in 1 11
print
if 5
break
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. For example:
:
( )
a =
if True
print 'Hello'
5
and

Incorrect indentation will result in .IndentationError
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
guring it out.
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.
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.
"""This is also a
perfect example of
multi-line comments"""
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.
We can have comments that extend up to multiple lines. One way is to use the hash( ) symbol
at the beginning of each line. For example:
#
Another way of doing this is to use triple quotes, either or .''' """

Docstrings in Python
A docstring is short for documentation string.
Output
Python docstrings (documentation strings) are the string literals that appear right after the
de nition of a function, method, class, or module.
Function to double the value
Triple quotes are used while writing docstrings. For example:
*num
:def double(num)
"""Function to double the value"""
return 2
Docstrings appear right after the de nition of a function, class, or a module. This separates
docstrings from multiline comments using triple quotes.
The docstrings are associated with the object as their attribute.__doc__
So, we can access the docstrings of the above function with the following lines of code:
*num
(double.__doc__)
:def double(num)
"""Function to double the value"""
return 2
print

Lesson 03 python statement, indentation and comments

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Lesson 03 python statement, indentation and comments