itertools chain python 3 code example

Example 1: python itertools repeat()

# How to use it:
# repeat(var, amount)

# repeat() is basically like range() but it gives an extra arg for a var

from itertools import repeat

for x in repeat("Spam? Or Eggs?", 3):
    print(x)
> "Spam? Or Eggs?"
> "Spam? Or Eggs?"
> "Spam? Or Eggs?"

Example 2: intertools combinations implementation

def combinations(iterable, r):
    # combinations('ABCD', 2) --> AB AC AD BC BD CD
    # combinations(range(4), 3) --> 012 013 023 123
    pool = tuple(iterable)
    n = len(pool)
    if r > n:
        return
    indices = range(r)
    yield tuple(pool[i] for i in indices)
    while True:
        for i in reversed(range(r)):
            if indices[i] != i + n - r:
                break
        else:
            return
        indices[i] += 1
        for j in range(i+1, r):
            indices[j] = indices[j-1] + 1
        yield tuple(pool[i] for i in indices)