(Python Tutorial – 002)
Python Statement, Indentation and Comments
In this tutorial, you will learn about Python statements, why indentation is important and use of comments in programming.
Python Statement
Instructions that a Python interpreter can execute are called statements. For example, a = 1
is an assignment statement. if
statement, for
statement, while
statement, etc. are other kinds of statements which will be discussed later.
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 = 1; b = 2; c = 3
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 unindented line. The amount of indentation is up to you, but it must be consistent throughout that block.
Generally, four whitespaces are used for indentation and are preferred over tabs. Here is an example.
for i in range(1,11):
print(i)
if i == 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:
if True:
print('Hello')
a = 5
and
if True: print('Hello'); a = 5
both are valid and do the same thing, but the former style is clearer.
Incorrect indentation will result in IndentationError
.
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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.
#This is a comment
#print out Hello
print('Hello')
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. For 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.
"""This is also a
perfect example of
multi-line comments"""
To learn more about comments, visit Python Comments.
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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):
"""Function to double the value"""
return 2*num
Docstrings appear right after the definition 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 __doc__
attribute.
So, we can access the docstrings of the above function with the following lines of code:
def double(num):
"""Function to double the value"""
return 2*num
print(double.__doc__)
Output
Function to double the value
To learn more about docstrings in Python, visit Python Docstrings.
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Disclaimer: The information and code presented within this recipe/tutorial is only for educational and coaching purposes for beginners and developers. Anyone can practice and apply the recipe/tutorial presented here, but the reader is taking full responsibility for his/her actions. The author (content curator) of this recipe (code / program) has made every effort to ensure the accuracy of the information was correct at time of publication. The author (content curator) does not assume and hereby disclaims any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from accident, negligence, or any other cause. The information presented here could also be found in public knowledge domains.
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