R function rep() in Python (replicates elements of a list/vector)

Question

The R function rep() replicates each element of a vector:

> rep(c(\"A\",\"B\"), times=2)
[1] \"A\" \"B\" \"A\" \"B\"

This is like the list m

Answer 1

Not sure if there's a built-in available for this, but you can try something like this:

>>> lis = ["A", "B"]
>>> times = (2, 3)
>>> sum(([x]*y for x,y in zip(lis, times)),[])
['A', 'A', 'B', 'B', 'B']

Note that sum() runs in quadratic time. So, it's not the recommended way.

>>> from itertools import chain, izip, starmap
>>> from operator import mul
>>> list(chain.from_iterable(starmap(mul, izip(lis, times))))
['A', 'A', 'B', 'B', 'B']

Timing comparions:

>>> lis = ["A", "B"] * 1000
>>> times = (2, 3) * 1000
>>> %timeit list(chain.from_iterable(starmap(mul, izip(lis, times))))
1000 loops, best of 3: 713 µs per loop
>>> %timeit sum(([x]*y for x,y in zip(lis, times)),[])
100 loops, best of 3: 15.4 ms per loop