Py Itertools — Free Python Tutorial
Learn Py Itertools in Python with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.
TL;DR: Learn Py Itertools in Python with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.
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Py Itertools in Python
itertools is a standard-library module of fast, memory-efficient iterator building blocks. All itertools return iterators (lazy evaluation) — they produce values on demand rather than building a full list, making them ideal for large data.
Infinite iterators: count(start, step) counts forever; cycle(iterable) loops forever; repeat(val, n) repeats n times. Always pair these with islice() or a break condition.
Combinatoric iterators: product() (Cartesian product), permutations(), combinations(), combinations_with_replacement(). Essential for brute-force search, combinatorics problems, and test data generation.
Terminating iterators: chain() links multiple iterables; groupby() groups consecutive equal keys; islice() slices any iterator; starmap() applies a function to each tuple; takewhile() / dropwhile() filter by predicate.
Py Itertools — Syntax
import itertools as it
it.count(1, 2) # 1, 3, 5, 7, … (infinite)
it.cycle("AB") # A, B, A, B, … (infinite)
it.chain([1,2],[3,4]) # 1, 2, 3, 4
it.islice(it.count(), 5)# 0, 1, 2, 3, 4
it.product("AB", repeat=2) # AA AB BA BB
it.permutations([1,2,3], 2) # (1,2)(1,3)(2,1)…
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