CodeQL documentation

Unnecessary lambda

ID: py/unnecessary-lambda
Kind: problem
Severity: recommendation
Precision: high
Tags:
   - maintainability
   - useless-code
Query suites:
   - python-security-and-quality.qls

Click to see the query in the CodeQL repository

A lambda that calls a function without modifying any of its parameters is unnecessary. Python functions are first class objects and can be passed around in the same way as the resulting lambda.

Recommendation

Remove the lambda, use the function directly.

Example

In this example a lambda is used unnecessarily in order to pass a method as an argument to call_with_x_squared.

import math

def call_with_x_squared(x, function):
    x = x*x
    return function(x)

print call_with_x_squared(2, lambda x: math.factorial(x))

This is not necessary as methods can be passed directly. They behave as callable objects.

import math

def call_with_x_squared(x, function):
    x = x*x
    return function(x)

print call_with_x_squared(2, math.factorial)

References