Python - Variable

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Python Identifier

• Identifier is a name given to a variable, function, or class.
• Identifier consists of one or more characters.

Following are rules for defining identifier

• Identifier can be the combination of upper case (A-z) letters or lower case letters or digits(0-9), underscore(_).
• It begins with the letter. For an instant, multy is the valid identifier and 23-bb is not a valid one.
• Keywords are not used as an identifier.
• Special symbols ($,%,@,!,#,) are not allowed except(_).
• An identifier can be of any length.

What is a Variable?

• Variable is a named memory location that refers to a value.
• If you want to define a variable means, you are going to reserve some space in memory for storing values.
• The python uses the '=' symbol to assign a value to the variable.
• This '=' symbol is known as the assignment operator.
• The Statement that assigns a value to the variable is known as the Assignment statement.

For example:
	a=10
Here the variable a is bound with a value of 10.

Python Variable Syntax

< variable_name> = < value >

In Python, There is no need to declare the variable in advance. Variables are declared and initialized by themselves at the time of assigning a value to the variable.

What is Value?

• Value is one of the basic things on which the program works, just like a number or letter.
• Value belongs to different data types such as integer, string, and floating point.
• If we want to know what type the value has, for this the interpreter uses the type() function.

For Example:
>> type(9)
<class 'int'>
>> type('10')
<class 'str'>
>> type(6.9)
<class 'float'>
>> type(True)
<class 'bool'>

Rules for defining Variable

• Variable names should be meaningful.
• Python's keywords are not used to define variables.
• Variable names should begin with a letter.
• Only underscore(-) is allowed to define variable.
• Variable names are case sensitive

For Example:
M=10
m='welcome'
print(m)
print(M)

Output:

10
Welcome

Python Keywords

• Keywords are the list of reserved words.
• Keywords have their own meanings.
• We can not use keywords as the variable name, function name, or constant name.
• If you are attempting to use the keyword as an identifier name, you will get an error message on the screen.

Following are the python keywords.

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