Python Keywords and Identifiers

1. What are Python Keywords

Keywords are reserved words in Python with predefined meanings that cannot be used as variable or function names.

import keyword

print(keyword.kwlist)

These words define Python’s syntax and control structures.

Examples: if, else, while, class, def, return, try, except, True, False, None

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2. List of Python Keywords (Core Examples)

import keyword

for word in keyword.kwlist:
    print(word)

Some commonly used keywords:

• Control Flow: if, elif, else, for, while, break, continue

• Function & Class: def, return, class, lambda

• Exception Handling: try, except, finally, raise

• Logical: and, or, not, is, in

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3. What are Identifiers

Identifiers are names used to identify variables, functions, classes, modules, or objects.

total = 100
def calculate_sum():
    pass

class User:
    pass

Here, total, calculate_sum, and User are identifiers.

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4. Rules for Identifiers

An identifier must:

• Start with a letter (a-z, A-Z) or underscore _

• Not start with a digit

• Contain letters, digits, or underscores only

• Not be a Python keyword

valid_name = 10
_invalid = 20
# 1value = 30  # Invalid

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5. Case Sensitivity in Identifiers

Python identifiers are case-sensitive.

value = 10
Value = 20

print(value)  # 10
print(Value)  # 20

value and Value are treated as two distinct identifiers.

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6. Invalid Identifier Examples

# 2data = 100      # Starts with digit (Invalid)
# class = 10       # Keyword (Invalid)
# my-name = 5      # Special character (Invalid)

Python enforces strict syntax rules for naming.

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7. Naming Conventions (PEP 8 Standard)

# Variable
total_price = 500

# Function
def calculate_total():
    pass

# Class
class UserAccount:
    pass

Standard practices:

• Variables & functions → snake_case

• Classes → PascalCase

• Constants → UPPER_CASE

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8. Difference Between Keywords and Identifiers

Feature	Keywords	Identifiers
Definition	Reserved words	User-defined names
Usage	Control Python syntax	Name variables, classes, functions
Customizable	No	Yes
Example	if, class	count, UserData

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9. Checking if a Word is a Keyword

import keyword

print(keyword.iskeyword("if"))      # True
print(keyword.iskeyword("value"))   # False

Useful for compilers, linters, and code validators.

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10. Real-World Naming Example

class OrderProcessor:
    def calculate_tax(self, amount):
        tax_rate = 0.18
        return amount * tax_rate

processor = OrderProcessor()
print(processor.calculate_tax(1000))

Demonstrates professionalism and readability using proper identifiers.

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Summary

Concept	Description
Keyword	Reserved word in Python
Identifier	User-defined name for entities
Naming Rules	Must follow syntax constraints
Case Sensitivity	Python is case-sensitive
Conventions	PEP 8 naming standards

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Best Practices

• Never use keywords as identifiers

• Follow PEP 8 naming conventions

• Use meaningful descriptive names

• Avoid single-character names in production code

• Maintain naming consistency throughout codebase

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Enterprise Importance

Correct use of identifiers and keywords ensures:

• Clean code readability

• Maintainability

• Lower bug rates

• Consistent team standards

• Scalable architecture

Critical in:

• Large-scale systems

• API design

• AI/ML pipelines

• Enterprise-grade applications

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