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
l = ['A','B'] n = [2, 4]
Your example uses strings which are already iterables. You can produce a result string which is similar to a list.
''.join([e * m for e, m in zip(l, n)]) 'AABBBB'
Update: the list comprehension is not required here:
''.join(e * m for e, m in zip(l, n)) 'AABBBB'