Performance Optimization with Pylint in Python

Performance optimization in Python is crucial for writing efficient code, especially when building large-scale applications. While Pylint is primarily known as a tool for checking the conformity of Python code against coding standards, it also provides some useful hints that can potentially optimize performance. In this article, we’ll look at how to utilize Pylint for performance improvements.

What is Pylint?

Pylint is a source-code, bug and quality checker for the Python programming language. It looks for programming errors, enforces a coding standard, and checks for certain types of code smells. It also offers simple ways to enforce a complete coding standard and configuration options for customized checks.

Setting up Pylint

Before diving into performance optimization, let’s set up Pylint:

  1. Install Pylint using pip:
    pip install pylint 
  2. Run Pylint on your script:

Performance Tips Highlighted by Pylint

While Pylint is not primarily a performance optimization tool, it can sometimes indicate potential performance pitfalls. Below are some examples:

1. Avoid Using Global Variables

Global variables can sometimes be a source of performance issues, especially when they are heavily manipulated in tight loops. Pylint can flag uses of global variables, which can serve as a hint to check if their usage affects performance.


counter = 0

def increment_counter():
    global counter
    counter += 1

Here, increment_counter modifies the global variable counter. If such a function is called often, this could be a performance bottleneck.

2. Limit the Use of Built-in Functions Inside Loops

Certain built-in functions can be expensive when called repeatedly within loops.

For instance, consider the following code:

for _ in range(1000000):
    my_list = list(range(10))

If Pylint detects a potential misuse or overuse of built-in functions, it may be worth considering moving such operations outside of tight loops, or seeking alternative solutions.

3. Avoid Unnecessary Comprehensions

Pylint can detect and warn about unnecessary list comprehensions. Such structures can lead to unnecessary memory allocations and iterations.


# This will generate a warning about unnecessary comprehension
result = [x for x in range(10) if x % 2 == 0]

A more optimized version:

result = list(range(0, 10, 2))

4. Built-in Data Types vs. Custom Objects

Pylint can hint when certain built-in data types might be more efficient than custom objects or structures. For instance, using sets for membership testing can be significantly faster than using lists. If your code checks membership in a list often, Pylint might hint at considering a set.

Manual Performance Review with Pylint Messages

Remember, Pylint won’t catch all performance issues. However, by carefully reviewing the messages and warnings given by Pylint, one can often identify code segments that might benefit from manual optimization.

For example, if Pylint identifies a complex method with too many branches or lines of code, it could be an indication that the method is doing too much. By breaking it down or refactoring, you could potentially optimize its performance.


Pylint is a powerful tool for ensuring code quality in Python. While its primary focus is on code standards and cleanliness, the hints and messages it provides can sometimes serve as starting points for performance optimization. It’s essential to use Pylint in conjunction with profiling tools and manual code review to truly optimize Python code performance.

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