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Python language has specified some rules for naming identifiers i.e. names given to variables, functions, classes, modules, etc. These rules are as follows :

• An identifier must start with an alphabet.
• An identifier cannot start with a digit.
• An identifier must not contain a space or a comma(,) or even a dot(.)
• A multi-word identifier can be separated by an underscore(_)
• An identifier could be a mix of lowercase(a-z), uppercase(A-Z) alphabets, digits(0-9) or an underscore(_).
• An identifier could be of any length.
• An identifier cannot contain special characters like #,@,&,%.
• Python is a case-sensitive language, hence identifier such as name is different from Name.
• Python keywords i.e. reserved words, should not be used as identifiers.

Python Naming Conventions

Python language has also specified some naming conventions for identifier i.e. names given to variables, functions, classes, modules, etc. Some of the general naming conventions are as follows:

Identifiers	Convention
Variable Name	A variable name should be in lowercase and a multiple word variable name is separated by underscore (_).
Function Name	A function name should be in lowercase alphabets and a multiple word variable name is separated by underscore (_) .
Class Name	A class name should be in CamelCase(where every first alphabet of a word is in uppercase, with no space or underscore in between multi-word class name.
Module Name	A module name should be in lowercase alphabets and a multi-word module name could be separated by an underscore (_).
Module Constant	A module constant should be in uppercase alphabets, where multi-word constant names are separated by an underscore(_).

Note: Not following these naming conventions while naming an identifier won't raise any error, but still, it is good to follow the naming conventions of Python when coding in it and it also improves the readability of a code.

An example of identifiers in a program :

Let us see a program with a set of valid identifiers.

# Python - Valid identifiers following naming conventions

size = 1000;
ink_price = 9.59;
string1 = 'a'
String1 = 'Have a beautiful life and keep smiling!'

print('Value referenced by variable size is : ', size)
print('Value referenced by variable ink_price is : ', ink_price)
print('Value referenced by variable string1 is : ', string1)
print('Value referenced by variable string2 is : ',  String1)

Output

Value referenced by variable size is :  1000
Value referenced by variable ink_price is :  9.59
Value referenced by variable string1 is :  a
Value referenced by variable string2 is :  Have a beautiful life and keep smiling!

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Keywords in Python

Keywords are the special words whose meaning is already defined in Python programming language. Keywords in Python are also known as reserved words because the name of any keyword cannot be used for an identifier such as variable, function, class name, etc in a Python program. There are about 32 keywords defined in Python. Let's see a table of these keywords.

keywords	keywords	keywords	keywords
False	None	True	and
class	continue	del	def
global	for	from	finally
is	lambda	nonlocal	not
with	while	return	try
as	elif	if	yield
or	assert	else	import
pass	break	except	in
raise

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Python variables and constants >

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