`operator` Module

Introduction

The operator module exports a set of efficient functions corresponding to the intrinsic operators of Python (like +, -, *, ==).

In interviews, this module is mainly used as a cleaner alternative to writing lambda functions when you need to pass an operation as an argument to another function (like sort() or reduce()).

Standard Math Operators

Instead of writing lambda x, y: x + y, you can pass operator.add.

import operator
from functools import reduce

nums = [1, 2, 3, 4]

# Using lambda
sum1 = reduce(lambda x, y: x + y, nums)

# Using operator (cleaner and slightly faster)
sum2 = reduce(operator.add, nums)

Common mathematical operators: - operator.add (+) - operator.sub (-) - operator.mul (*) - operator.truediv (/) - operator.floordiv (//)

Item Getters

The most common use of the operator module in interviews is itemgetter.

When sorting a list of tuples or dictionaries, you often need to sort by a specific index or key. itemgetter creates a fast, C-optimized callable that fetches that item.

from operator import itemgetter

inventory = [
    ('apple', 3, 100),
    ('banana', 1, 50),
    ('orange', 2, 75)
]

# Sort by the 2nd element (quantity)
# Equivalent to: key=lambda x: x[1]
inventory.sort(key=itemgetter(1))
print(inventory)
# [('banana', 1, 50), ('orange', 2, 75), ('apple', 3, 100)]

# Sort by the 3rd element, then the 1st
inventory.sort(key=itemgetter(2, 0))

When to use `itemgetter` vs `lambda`

For simple indices, itemgetter(1) is preferred because it is faster (executed entirely in C) and cleaner than lambda x: x[1]. However, if you need to perform any math or complex logic on the element before sorting, you must use a lambda.

Summary

Use operator.add, mul, etc., as arguments to reduce().
Use operator.itemgetter(idx) as the key function for sorting lists of tuples/lists.
itemgetter is generally faster and cleaner than writing a lambda for simple index fetching.

operator Module