Python Keywords and Identifiers

Python uses keywords and identifiers to create and organize programs. Keywords are predefined words that Python recognizes and reserves for specific purposes, while identifiers are names created by programmers to represent variables, functions, classes, and other objects.

Keywords

Keywords are predefined words that Python recognizes as part of its syntax. They are used to perform specific tasks, such as defining functions, controlling program flow, and handling exceptions.

• Written in lowercase, except True and False.
• Cannot be used as identifiers, variables, or function names.
• Python 3.11 has 35 keywords.

The keyword module provides:

• iskeyword(): checks if a string is a keyword.
• kwlist: returns the list of all keywords.

Rules for Keywords in Python

• Python keywords cannot be used as identifiers.
• All the keywords in Python should be in lowercase except True and False.

List of Python Keywords

Getting List of all Python keywords

List of all the keyword names can be accessed using the below code:

['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is',...

Identifiers

Identifiers are user-defined names used to identify and reference program elements such as variables, functions, classes, modules, and objects. They help programmers organize and access different components of a program and must follow Python's naming rules.

• Can include letters, digits, and underscores (_).
• Case-sensitive: num, Num, and NUM are different identifiers.
• Python provides str.isidentifier() to check if a string is a valid identifier.

Note: An identifier is a general name used for variables, functions, classes, and other objects in Python, whereas a variable is a specific type of identifier used to store data. Therefore, every variable is an identifier, but not every identifier is a variable.

Rules for Naming Python Identifiers

• It cannot be a reserved python keyword.
• It should not contain white space.
• It can be a combination of A-Z, a-z, 0-9, or underscore.
• It should start with an alphabet character or an underscore ( _ ).
• It should not contain any special character other than an underscore ( _ ).

Examples of Python Identifiers

Valid identifiers:

• var1
• _var1
• _1_var
• var_1

Invalid Identifiers

• !var1
• 1var
• 1_var
• var#1
• var 1

Python Keywords and Identifiers Examples

Example 1: Example of and, or, not, True, False keywords.

example of True, False, and, or, not keywords
True
True
True

Example 2: Example of a break, continue keywords and identifier.

1
2
3
4
5

Example 3: example of for, in, if, elif, and else keywords.

One
Two
else block execute
else block execute

Example 4: def, if and else keywords.

given number is even

Example 5: Example of try, except, raise.

0.1
Exception raises
None

Example 6: Example of a lambda keyword.

2
3
4
5
6

Example 7: use of return keyword.

5

Example 8: use of a del keyword.

['a', 'b', 'c', 'd', 'e']
['a', 'b', 'd', 'e']

Example 9: use of global keyword.

10

Example 10: example of yield keyword.

1
2
3
4
5
6

Example 11: Use of assert keyword.

Output:

AssertionError: List is empty.

Example 12: Use of pass keyword

Example 13: Use of finally keyword 

Inside try block
Inside finally block
Inside Exception block
Inside finally block

Example 14: Use of import keyword

factorial of 5 is : 120

Example 15: Use of "is" keyword 

True
False

Example 16: Use of from keyword 

gcd of 345 and 675 is : 15

Example 17: Use of async and await keyword 

120

Explanation:

• The async keyword is used to define an asynchronous function, allowing it to pause and resume execution without blocking the entire program.
• The await keyword pauses the execution of an asynchronous function until the awaited task is completed.
• When factorial(5) is called, it recursively calculates the factorial of 5 and returns the result.