Efficient Looping: range

• Creating large lists for loops is memory-intensive (e.g., list(range(1_000_000))).
• range() stores only start, stop, and step values, not all numbers.
• Numbers are generated one at a time during iteration, reducing memory usage.
• Ideal for loops needing a fixed number of iterations without large allocations.

import sys

number_count = 10_000_000

numbers_list = list(range(number_count))
numbers_range = range(number_count)

list_mb = sys.getsizeof(numbers_list) / (1024**2)
range_mb = sys.getsizeof(numbers_range) / (1024**2)

print(f"List size: {list_mb:.2f}")
print(f"Range size: {range_mb:.6f}")
print(f"List uses {(list_mb / range_mb):.2f} more memory!")

Using range()

• range(stop): iterate from 0 up to (but not including) stop.
• range(start, stop): iterate from start up to stop.
• range(start, stop, step): iterate with a custom step increment.

for i in range(5):
    print(f"Retry #{i}")

for year in range(2020, 2024):
    print(f"Processing logs for {year}")

for server_id in range(10, 30, 5):
    print(f"Checking server {server_id}")

Getting Index + Value: enumerate()

• Use enumerate(iterable, start=0) to get (index, item) tuples.
• The start parameter sets the initial index value.

servers = ["web01", "web02", "web03"]

for idx, server in enumerate(servers, 1):
    print(f"#{idx}: Processing server {server}")

Parallel Iteration: zip()

• Use zip(*iterables) to pair items from multiple iterables.
• Iteration stops when the shortest iterable is exhausted.

hosts = ["hostA", "hostB", "hostC"]
ips = ["10.0.0.1", "10.0.0.2"]
azs = ["us-east-1a", "us-east-1b"]

for host, ip, az in zip(hosts, ips, azs):
    print(f"Host: {host}, IP: {ip}, AZ: {az}")