Identifiers in Python: Naming Rules & Best Practices

Identifiers in Python are names you assign to variables, functions, classes, or modules. They help the interpreter and developers identify elements in your code. Each identifier must follow specific naming rules and conventions to keep your code readable, organized, and error-free. 

In this guide, you’ll read more about what identifiers in Python are, their naming rules, and key conventions based on PEP 8. You’ll also explore valid and invalid identifiers, best naming practices, common mistakes, and ways to validate identifiers programmatically. 

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What is an Identifier in Python? 

An identifier in Python is the name you use to identify variables, functions, classes, and other objects in your code. Every value or object in Python must have a name so you can refer to it later. These names are called identifiers. 

Identifiers help the interpreter and programmers recognize what each element represents. For example, when you write name = "Alice", the word name is the identifier that points to the string "Alice". 

Think of identifiers as labels that give meaning to your data and logic. Without them, your code would be unreadable and hard to manage. 

Why Identifiers Matter 

Identifiers are essential for three main reasons: 

• They make code readable and organized. 
• They help avoid confusion between different parts of your program. 
• They allow reuse of logic through named functions and classes. 

Identifiers create a clear mapping between your logic and the data it handles, which is crucial for debugging and collaboration. 

The importance of Python identifiers goes beyond just naming conventions; it’s about how they structure your code and help manage different components of your program. Here are three programs that can help you: 

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Examples of Identifiers in Python 

You can use identifiers for many purposes: 

Each of these examples shows how identifiers give names to different elements in Python code. 

How Identifiers Work 

Identifiers act as references. When you create one, Python stores it in memory and associates it with the value or object you assign. For example: 

x = 10 
y = x + 5 
  

Here, x refers to the value 10, and y uses that reference to create a new value 15. The identifiers x and y make the code meaningful to both Python and humans. 

Identifier vs Variable vs Keyword 

These terms often confuse beginners. The table below clears that up: 

In short, all variables are identifiers, but not all identifiers are variables. 

Also read: A Comprehensive Guide to Understanding the Different Types of Data in 2025 

Naming Identifiers in Python 

Identifiers can include: 

• Letters (A–Z, a–z) 
• Digits (0–9) 
• Underscore (_) 

But remember: 

• You cannot start an identifier with a digit. 
• Python identifiers are case-sensitive (Name and name are different). 
• You cannot use reserved keywords as identifiers. 

For example: 

# Valid identifiers 
name = "Rahul" 
age1 = 25 
_user = "Admin" 
 
# Invalid identifiers 
1name = "Rahul"   # starts with a number 
for = 10          # reserved keyword 
  

 Key Points to Remember 

• Identifiers help name data, functions, and objects. 
• They must follow Python’s naming rules. 
• They make your code more readable and maintainable. 
• They are case-sensitive and must not use reserved keywords. 

Using identifiers correctly is the foundation of writing clean, understandable Python code. 

Also Read: Libraries in Python Explained: List of Important Libraries 

Rules for Naming Identifiers in Python 

Identifiers in Python follow a set of rules that keep your code clean and error-free. These rules help both Python and developers understand your program’s structure. If you don’t follow them, you’ll get syntax errors or unexpected results. 

Let’s break down the main naming rules you should always remember. 

1. Identifiers Can Contain Letters, Digits, and Underscores 

You can use alphabets (A–Z, a–z), numbers (0–9), and the underscore _ character in an identifier. 

user_name = "Rahul" 
count1 = 100 
data_2025 = "Sample" 
  

These are valid because they use allowed characters. 

2. Identifiers Cannot Start with a Digit 

You can include digits but never at the beginning. 

1name = "Rahul"   # Invalid 
name1 = "Rahul"   # Valid 
  

Python raises an error if an identifier starts with a number. 

3. Identifiers Are Case-Sensitive 

Python treats uppercase and lowercase letters as different. 

Name = "Rahul" 
name = "Amit" 
  

Here, Name and name are two different identifiers. 

Also Read: Types of Data Structures in Python That Every Coder Should Know! 

4. Reserved Keywords Cannot Be Used as Identifiers 

Python has predefined words used for control flow and syntax. These keywords cannot be reused as identifiers. 

You can check all reserved keywords using the following code: 

import keyword 
print(keyword.kwlist) 
  

5. Identifiers Cannot Include Special Characters 

Characters like @, #, $, %, or spaces are not allowed. 

user@name = "Rahul"  # Invalid 
user_name = "Rahul"  # Valid 
  

Only underscores are allowed to separate words in an identifier. 

6. Use Underscore for Multi-Word Identifiers 

If an identifier has more than one word, separate them using underscores for better readability. 

student_name = "John" 
total_score = 85 
  

This naming pattern is called snake_case, and it’s part of Python’s PEP 8 style guide. 

7. Avoid Built-in Function Names 

Never name identifiers after Python’s built-in functions. Doing so can override them. 

list = [1, 2, 3]   # Avoid 
print = "Hello"    # Avoid 
  

If you accidentally override a built-in name, you’ll lose access to that function until you restart your program. 

8. Identifiers Should Be Descriptive 

Choose names that describe the purpose of the variable or function. This makes code easier to understand. 

# Clear naming 
total_marks = 480 
average_score = total_marks / 5 
  

Avoid using single-letter identifiers except in loops or short expressions. 

Also Read: GitHub Project on Python: 30 Python Projects You’d Enjoy 

Summary Table: Identifier Naming Rules 

 Key Takeaways 

• Identifiers must start with a letter or underscore. 
• They can contain letters, numbers, and underscores only. 
• Python identifiers are case-sensitive. 
• Avoid reserved keywords and built-in function names. 
• Use readable, descriptive names for better clarity. 

Python Identifier Naming Conventions 

Beyond basic naming rules, Python follows certain naming conventions that make code readable and consistent across projects. These conventions are not strict requirements, but they are part of Python’s PEP 8 style guide, which most developers follow. Understanding and applying these conventions helps you write code that looks clean, professional, and easy to maintain. 

1. Follow PEP 8 Naming Guidelines 

PEP 8 defines how you should name identifiers in Python, including variables, constants, functions, and classes. 

 Here are the key standards: 

These conventions make your code predictable and easy for others to read. 

2. Use Snake Case for Variables and Functions 

Variables and functions typically follow snake_case, where words are separated by underscores. 

def calculate_average(): 
    total_score = 90 
    return total_score / 3 
  

This is the standard way to name identifiers in Python because it improves readability. 

Also Read: Top 6 Python IDEs of 2025 That Will Change Your Workflow! 

3. Use Pascal Case for Classes 

Class names follow PascalCase, where the first letter of each word is capitalized. 

class StudentRecord: 
    pass 
  

This makes classes stand out from functions and variables. 

4. Use Uppercase for Constants 

Constants are identifiers whose values should not change. They are written in UPPERCASE_WITH_UNDERSCORES. 

PI = 3.14159 
MAX_CONNECTIONS = 10 
  

Although Python doesn’t enforce constants, writing them in uppercase signals that they should remain unchanged. 

5. Prefix Private Identifiers with Underscores 

To indicate that an identifier is meant for internal use only, prefix it with an underscore _. 

_internal_value = 25 
  

For stronger privacy, use double underscores __, which trigger name mangling to protect the variable. 

class BankAccount: 
    __balance = 1000 
 

Key Takeaways 

• Follow PEP 8 to maintain clean and readable code. 
• Use snake_case for variables and functions. 
• Use PascalCase for class names. 
• Use uppercase for constants. 
• Prefix private identifiers with underscores. 
• Stay consistent across your entire codebase. 

Applying these Python identifier naming conventions makes your code more professional, structured, and easier for others to understand. 

Also Read: Top 70 Python Interview Questions & Answers: Ultimate Guide 2025 

Best Practices for Naming Identifiers in Python 

Following best practices for naming identifiers in Python ensures your code is readable, maintainable, and less error-prone. 

• Be Descriptive: Use meaningful names that clearly indicate the purpose of the variable, function, or class. 

total_marks = 95   # Good 
x = 95             # Avoid 
  

• Follow Conventions: Stick to snake_case for variables and functions, PascalCase for classes, and UPPERCASE for constants. 
• Avoid Reserved Keywords: Never use Python keywords as identifiers. 

for = 10   # Invalid 
count = 10 # Valid 
  

• Use Consistent Naming: Keep naming patterns uniform throughout your project for clarity. 
• Avoid Confusing Names: Do not reuse built-in function names like list, str, or sum. 
• Use Underscores for Private Identifiers: Prefix internal-use variables with _ to indicate privacy. 

Implementing these practices ensures your identifiers in Python remain clear, professional, and error-free. 

Also Read: Inheritance in Python: Types, Best Practices & Examples 

Common Mistakes with Identifiers 

Many beginners make avoidable errors when using identifiers in Python. Recognizing these mistakes helps write cleaner code. 

• Starting with Numbers: Identifiers cannot begin with a digit. 

1name = "Alice"  # Invalid 
name1 = "Alice"  # Valid 
  

• Using Reserved Keywords: Python keywords like for, if, or class cannot be identifiers. 
• Overwriting Built-ins: Avoid names like list, sum, or str. 
• Including Special Characters or Spaces: Only letters, digits, and underscores are allowed. 

user-name = "Rahul"  # Invalid 
user_name = "Rahul"  # Valid 
  

• Inconsistent Naming: Switching between snake_case and camelCase reduces readability. 
• Unclear or Short Names: Names like x or temp do not convey meaning. 

Avoiding these mistakes ensures your identifiers in Python are valid, readable, and maintainable. 

Learn Best Practices for Naming Identifiers in Python with upGrad 

Identifiers in Python follow specific naming rules that help ensure code clarity and prevent errors. By adhering to best practices, such as using uppercase for constants and following appropriate naming conventions for variables, functions, and classes, you can improve the readability and maintainability of your code. 

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To help bridge this gap, upGrad’s personalized career guidance can help you explore the right learning path based on your goals. You can also visit your nearest upGrad center and start hands-on training today! 

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