MemoryError: Creating Large List

Why This Happens

Creating a list with billions of elements consumes massive memory. range() is lazy and uses constant memory. Generator expressions also produce values lazily.

The Problem

numbers = list(range(1_000_000_000))

The Fix

for n in range(1_000_000_000):
    process(n)

# Generator expression instead of list comprehension:
total = sum(x**2 for x in range(1_000_000_000))

Step-by-Step Fix

1. 1

   Use range() directly

   Iterate over range() without converting to list.

2. 2

   Use generator expressions

   Replace [x for x in items] with (x for x in items).

3. 3

   Use itertools

   Functions like itertools.islice() process data lazily.