Writing clean, efficient, and error-free code is crucial for any Python developer. One of the best tools for maintaining high code quality is Pylint — a powerful static code analyzer for Python. Let’s dive into how Pylint works, the types of errors it catches, and how we can improve our code using it.

What is Pylint?

Pylint is a static code analysis tool for Python 2 and 3, with its latest version supporting Python 3.8.0 and above. It analyzes your code without running it and checks for:

• Errors in the code
• Coding standard violations
• Code smells (areas that need refactoring)
• Suggestions for better code structure

Pylint also gives your code a score out of 10 based on the number and severity of issues present.

Types of Errors in Pylint

Pylint categorizes issues into five distinct types:

• C: Convention — Violations of coding style and best practices
• R: Refactor — Code that could be simplified or restructured for clarity
• W: Warning — Potential issues that might not stop execution but are problematic
• E: Error — Clear programming mistakes
• F: Fatal — Serious errors that prevent Pylint from running

Let’s see Pylint in action with some examples.

Example

# Write a Python program that takes two integers as input and performs division (num1 / num2). Handle the ZeroDivisionError and display a custom error message when the second number is zero.
import logging

logging.basicConfig(
    filename="exception_handling.log", encoding="utf-8", level=logging.DEBUG
)

try:
    num1 = int(input("Enter first number: "))
    num2 = int(input("Enter second number: "))
    result = num1 / num2
    print(result)
except ZeroDivisionError as e:
    logging.error(e)

# Write a Python program that takes user input for age. Create a custom exception InvalidAgeError to handle cases where the age is below 0 or above 120.
class InvalidAgeError(Exception):
    pass


try:
    age = int(input("Enter your age: "))
    if age < 0 or age > 120:
        raise InvalidAgeError("Age must be between 0 and 120")
    print(age)
except InvalidAgeError as e:
    logging.error(f"{e}")Example 2: Custom Exception for Age Validation

Pylint Analysis and Results

When we examine above code using the pylint, we get different errors as given below. Our current score is 6.67.$ pylint 1_exception_handling.py

We get several errors and warnings:

$ pylint 1_exception_handling.py 
************* Module 1_exception_handling
1_exception_handling.py:1:0: C0301: Line too long (190/100) (line-too-long)
1_exception_handling.py:16:0: C0301: Line too long (152/100) (line-too-long)
1_exception_handling.py:1:0: C0114: Missing module docstring (missing-module-docstring)
1_exception_handling.py:1:0: C0103: Module name "1_exception_handling" doesn't conform to snake_case naming style (invalid-name)
1_exception_handling.py:17:0: C0115: Missing class docstring (missing-class-docstring)
1_exception_handling.py:27:4: W1203: Use lazy % formatting in logging functions (logging-fstring-interpolation)

------------------------------------------------------------------
Your code has been rated at 6.67/10 (previous run: 7.22/10, -0.56)Our initial Pylint score is 6.67/10.

Fixing the Errors

Let’s fix these issues step by step:

• line-too-long: Break long lines into multiple lines
• missing-module-docstring: Add a docstring at the top of the module
• invalid-name: Rename the module to follow snake_case convention
• missing-class-docstring: Add a docstring to the InvalidAgeError class
• logging-fstring-interpolation: Use %s formatting instead of f-strings in logging

Here’s the refactored code:

"""
Exception Handling Assignments
"""

# Write a Python program that takes two integers as input and performs division (num1 / num2).
# Handle the ZeroDivisionError and display a custom error message when the second number is zero.

import logging

logging.basicConfig(
    filename="exception_handling.log", encoding="utf-8", level=logging.DEBUG
)

try:
    num1 = int(input("Enter first number: "))
    num2 = int(input("Enter second number: "))
    result = num1 / num2
    print(result)
except ZeroDivisionError as e:
    logging.error("%s", e)


# Write a Python program that takes user input for age.
# Create a custom exception InvalidAgeError to handle cases where the age is below 0 or above 120.
class InvalidAgeError(Exception):
    """custom exception class for invalid age input"""


try:
    age = int(input("Enter your age: "))
    if age < 0 or age > 120:
        raise InvalidAgeError("Age must be between 0 and 120")
    print(age)
except InvalidAgeError as e:
    logging.error("%s", e)import logging

Final Pylint Score

Running Pylint again:

$ pylint exception_handling.py 

--------------------------------------------------------------------
Your code has been rated at 10.00/10 (previous run: 10.00/10, +0.00)

🎉 Perfect score!

Conclusion

Using Pylint regularly helps maintain clean, readable, and efficient Python code. It enforces best practices, catches errors early, and suggests improvements — making you a better developer in the long run. Start integrating Pylint into your workflow and aim for that perfect 10/10!