Python | Python syntax

Python | Python syntax

Python is an interpreted, object-oriented programming language similar to PERL, that has gained popularity because of its clear syntax and readability. Python is said to be relatively easy to learn and portable, meaning its statements can be interpreted in a number of operating systems.

Comment

Comments are used to document and are ignored by the compiler.

In python, comments are of two types. That is,

·        Single line comment

·        Multi-line comments

Single line comments

In python, all comment characters are written after the # sign.

Example

# Python Basic Syntax - Example Program # We are comments

Multiline Comment in Python

Multiline starting commenting code is ''' and ending with same, that is '''.

Example

''' This     is    multiline     comment ''' ''' Multiline comment     starts with \'''     and ends with     \''' '''

Printing statement

General form to use print statement in python.

print("any character or string");

In the above syntax of print statement, print is the keyword, opening (" and closing ") followed by ; are the syntax to write print statement in python to successfully output any required combination of characters on the output screen.

Variables

Variables in Python, are the reserved memory locations to store the values in a Python program. To create a variable and assign some values to it, follow the given syntax or general form in Python.

variable_name = "value to be assign";

You can also say that the above statement is called as assignment statement. In the above statement variable_name is the name of the variable, and the value is assine inside “ and “ sign.

Operators

Operators in Python, are used to perform mathematical and logical operations. There are the following types of operators available in Python:

• Arithmetic Operators
• Logical Operators
• Comparison (Relational) Operators
• Assignment Operators
• Bitwise Operators
• Membership Operators
• Identity Operators

Arithmetic operators

Operator	Name	Meaning
+	Addition Operator	Add two values
-	Subtraction Operator	Used for subtraction
*	Multiplication Operator	Used for multiplication
/	Division Operator	Used for division
%	Modulus Operator	Returns remainder after dividing
//	Floor Division Operator	Returns the quotient without any digits after decimal
**	Exponent Operator	Used to perform exponential calculation on operators

Comparison operators

Operator	Meaning
==	Returns true if values of the two operands are equal, otherwise returns false if not equal
!=	Returns true if value of the two operands are not equal, otherwise returns false if equal
>	Returns true if value of the left operand is greater than right one, otherwise false if value of the right operand is greater than left one
<	Returns true if value of the left operand is less than right one, otherwise false if value of the right operand is less than left one
>=	Returns true if value of the left operand is greater than or equal to the value of the right one, otherwise false if value of the right operand is greater than left one
<=	Returns true if value of the left operand is less than or equal to right one, otherwise false if value of the right operand is less than or equal to left one

Assignment operators

Operator	Name	Meaning
=	Simple Assignment Operator	Used for assigning values
+=	Add and Assignment Operator	This operator adds the right operand to the left operand and assigns the result to the left operand
-=	Subtract and Assignment Operator	This operator subtracts the right operand from the left operand and then assigns the result to the left operand
/=	Divide and Assignment Operator	This operator divides the left operand with the right operand and then assigns the result to the left operand
*=	Multiply and Assignment Operator	This operator multiplies the right operand with the left operand and then assigns the result to the left operand
**=	Exponent and Assignment Operator	This operator performs the exponential calculation on operators and then assign the value to the left operand
%=	Modulus and Assignment Operator	This operator takes modulus using the two operands and then assigns the result to the left operand
//=	Floor Division and Assignment Operator	This operator performs the floor division on the operators and then assign the value to the left operand

Bitwise operators    

Operator	Name	Meaning
&	Binary AND Operator	This operator copies a bit to the result only if its exists in both the operands
^	Binary OR Operator	This operator copies a bit only if it exists in either the operand
|	Binary XOR Operator	This operator copies the bit only if it is the set of one operand but not the both
~	Binary Ones Complement Operator	This is unary operator, has the effect of 'flipping' bits
>>	Binary Right Shift Operator	The left operand's value is moved right by the number of bits specified by the right operand
<<	Binary Left Shift Operator	The left operand's value is moved left by the number of bits specified by the right operand

 Logical operators

Operator	Name	Meaning
and	Logical AND Operator	If both the operands are true, then the condition becomes true, otherwise false
not	Logical NOT Operator	This operator used to reverse the logical state of its operand
or	Logical OR Operator	If any of the two operands are non-zero, then the condition becomes true, otherwise false

Import statement

The import statement is used to import or load modules (modules are files, contains code to be used in other program just by importing that module using the import statement), for example, to load random module,

 General form.

import random

Example

import random val1 = random.randrange(100); val2 = random.randrange(100); print("Following are the two generated random numbers \ under 100."); print("First: ",val1); print("Second: ",val2);

Function

A function in python, is a block of code, used to perform a particular action.

Rules for defining a function

To define a function in python, follow these rules:

• function blocks in python, begins with the keyword def, followed by the function name and then parentheses
• the parameters/arguments should be placed inside these parentheses
• the code block of the function starts with a colon (:)
• and now the return statement exits a function, passing back an expression to the function caller
• a return statement with no any arguments is the same as return None

General form

def function_name(parameters):                "function_doc_string"                function_suite                return [expression]

Example

def printit(strn):                     "This will print the passed string into this function"                     print(strn)                     return

Decision making statement

Decision-making statements in python help in controlling your program accordingly. There are the following decision-making statements available in Python:

• if statement

General form

if expression:             statement(s)

• if-else statement

General form

if expression:                     statement(s) else:                     statement(s)

• nested if statement

General form

if expression1:                statement(s)                if expression2:                                statement(s)                elif expression3:                                statement(s)                else:                                statement(s) else:                statement(s)

Loops

Loops in Python are used to control your program. Loops are basically used to execute a block of code several numbers of times accordingly. There are the following types of loops available in Python:

• for loop

general form

for iterating-var in sequence:                     statement(s)

• while loop

General form

while expression: statement(s)

• nested loop

General form (nested for loop)

for iterating-var in sequence:                for iterating-var in sequence:                                statement(s)                statement(s)

     General form (nested while loop)

while expression:    while expression:       statement(s)    statement(s)