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Saturday, July 16, 2022

Python Syntax & Comments

Syntax

One of the biggest advantages of Python is it's syntax. It is easy to read, write and understand. 

In this article, I'm going to cover the below in brief.
  • Comments - How to write single line and multi line comments in Python
  • Variable definition - How to define variables in Python
  • End of statement - How does Python identify the end of a statement
  • Indentation - How integrated is indentation in Python syntax.

Comments

Comments are important part of any programming language. Python has two different ways of writing comments in the code. 
  • Multi-line comments 
  • Single-line comments 
Multi-line comments can be written by mentioning three quotes (''') at the beginning and ending of the comment.  

E.g.:

'''
Multiple lines of comments
Usually written at the start of a program/function
describing usage of the program/function
'''

Multi-line comments are helpful when we need to write few lines of comments to describe about a block of code, a function or a program. 

Single-line comments can be written with # and comment would end with End of line. 

# Single line comments end with End of Line
print("Hello...") # Print Hello

Variable Definition

Python is dynamically typed language and doesn't require variables to be defined with a specific data type. Python identifies the data type automatically based on the data passed into the variable. 

E.g.: 

a = 10  # Integer
b = "B" # String

End Of Statement

Unlike most of other programming languages, Python doesn't use/require a semicolon (;) to indicate end of statement. End of line (CR LF) is usually considered and end of statement. 

E.g.: 

a = 10
b = "B"

As soon as end of line is detected, Python assumes the end of statement and considers the next line as the next statement. 

We can also terminate a statement with semicolon (;). This usually helpful when we need to write multiple statements in a single line. 

a = 10; b = "B"

What if the statement is too big and has to extend beyond a line? Using '\' at the end of the line would help if a statement is going beyond single line. 

c = "This is a big statement " \
"and has to extend beyond single line."

d = a/2 +\
100

Above two statements are equal to the below. 

c = "This is a big statement and has to extend beyond single line."

d = a/2 + 100

This can also be done by enclosing with in parenthesis. 

c = ("This is a big statement " +
"and has to extend beyond single line.")

d = (a / 2 +
100)

Indentation

Indentation is recommended in any programming language to make the code easy to understand. In Python, indentation is mandatory to indicate/write a block of code. 

There is no restriction on how many spaces are to be used, but number of spaces need to be consistent in a block of code. But, 4 spaces are widely used.

# This function uses 4 blank spaces
def printA():
a = 10
print(a)

# This function uses 2 blank spaces
def printB():
b = "B"
print(b)

But, we cannot have different spaces in the same block of code. 

# This function uses 4 blank spaces
def printA():
a = 10
print(a)

Having different number of spaces would cause the program to throw IndentationError (IndentationError: unindent does not match any outer indentation level) 

A block of code doesn't necessarily be a function, it can also be a condition or loop. 

# This function uses 4 blank spaces
def printA():
a = 10
b = 20

# This condition uses 2 blank spaces
if (a > b):
print("a is greater than b")
# Code with in else block uses 8 blank spaces
else:
print("b is greater than a")

In the above code, 
  • Statements with in printA function including if and else, are to follow the same indentation. 
  • Any code under if or else need to use the same indentation. 
One thing to note here is, A block of code would always be preceded by colon (:).


Hope the above content has been of some help to you. 

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