Reserved Words

Python reserved words (keywords) are special words that have predefined meanings and cannot be used as variable names, function names, or any other identifiers. This reference provides a complete list of all Python keywords with their purposes and usage examples.

Python Keywords Reference

Keyword	Purpose	Category	Usage Example	Description
and	Logical operator	Operator	`if x > 0 and y > 0:`	Logical AND operation
as	Alias creation	Statement	`import numpy as np`	Create alias for imports or with statements
assert	Debugging aid	Statement	`assert x > 0, "x must be positive"`	Test conditions during development
break	Loop control	Control Flow	`break`	Exit current loop immediately
class	Class definition	Definition	`class MyClass:`	Define a new class
continue	Loop control	Control Flow	`continue`	Skip to next iteration of loop
def	Function definition	Definition	`def my_function():`	Define a new function
del	Object deletion	Statement	`del my_variable`	Delete objects or variables
elif	Conditional	Control Flow	`elif condition:`	Additional condition in if statement
else	Conditional/Loop	Control Flow	`else:`	Alternative branch in if or loop
except	Exception handling	Exception	`except ValueError:`	Handle specific exceptions
False	Boolean value	Literal	`is_valid = False`	Boolean false value
finally	Exception handling	Exception	`finally:`	Code that always executes
for	Loop construct	Control Flow	`for item in list:`	Iterate over sequences
from	Import statement	Import	`from math import sqrt`	Import specific items from module
global	Scope declaration	Scope	`global my_var`	Declare global variable in function
if	Conditional	Control Flow	`if condition:`	Basic conditional statement
import	Module import	Import	`import os`	Import modules or packages
in	Membership test	Operator	`if item in list:`	Test membership in sequence
is	Identity test	Operator	`if x is None:`	Test object identity
lambda	Anonymous function	Function	`lambda x: x * 2`	Create small anonymous functions
None	Null value	Literal	`result = None`	Represents absence of value
nonlocal	Scope declaration	Scope	`nonlocal my_var`	Access enclosing scope variable
not	Logical operator	Operator	`if not condition:`	Logical NOT operation
or	Logical operator	Operator	`if x or y:`	Logical OR operation
pass	Placeholder	Statement	`pass`	Empty placeholder statement
raise	Exception raising	Exception	`raise ValueError("message")`	Raise exceptions manually
return	Function return	Statement	`return result`	Return value from function
True	Boolean value	Literal	`is_valid = True`	Boolean true value
try	Exception handling	Exception	`try:`	Begin exception handling block
while	Loop construct	Control Flow	`while condition:`	Create while loops
with	Context manager	Statement	`with open(file) as f:`	Resource management
yield	Generator	Function	`yield value`	Create generator functions

Keyword Categories

Control Flow Keywords

Keywords that control the flow of program execution:

if, elif, else: Conditional execution
for, while: Loop constructs
break, continue: Loop control
pass: Empty placeholder

Function and Class Definition

Keywords for defining reusable code blocks:

def: Function definition
class: Class definition
lambda: Anonymous functions
return: Return values
yield: Generator functions

Exception Handling

Keywords for managing errors and exceptions:

try, except, finally: Exception handling blocks
raise: Manually raise exceptions
assert: Debug-time assertions

Import and Module Keywords

Keywords for working with modules:

import: Import modules
from: Import specific items
as: Create aliases

Scope and Variable Keywords

Keywords affecting variable scope:

global: Global variable declaration
nonlocal: Enclosing scope variable access
del: Delete variables or objects

Logical and Comparison Operators

Keywords for logical operations:

and, or, not: Logical operators
in: Membership testing
is: Identity testing

Literal Values

Keywords representing fixed values:

True, False: Boolean literals
None: Null value literal

Context Management

Keywords for resource management:

with: Context manager protocol

Common Usage Patterns

Conditional Execution

# Basic if-elif-else structure
age = 25
if age >= 18:
    print("Adult")
elif age >= 13:
    print("Teenager")
else:
    print("Child")

Loop Constructs

# For loop with break and continue
for i in range(10):
    if i == 3:
        continue  # Skip 3
    if i == 7:
        break     # Stop at 7
    print(i)

Exception Handling

try:
    # risky code
except SpecificError as e:
    # handle specific error
except Exception as e:
    # handle general errors
finally:
    # cleanup code

Function Definition

# Function with global variable
counter = 0

def increment():
    global counter
    counter += 1
    return counter

print(increment())  # 1
print(increment())  # 2

Class Definition

class ClassName:
    def __init__(self):
        pass
    
    def method(self):
        return value

Important Notes

Case Sensitive: All keywords are lowercase and case-sensitive
Reserved: Cannot be used as identifiers (variable names, function names, etc.)
Version Specific: Some keywords may be added in newer Python versions
Syntax Highlighting: Most editors highlight keywords in different colors
Error Prevention: Using keywords as identifiers will raise SyntaxError

Online Python

Reserved Words

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