epic-capybara/epic_capybara/util.py

0001 from itertools import chain, cycle, dropwhile, starmap, tee
0002
0003
0004 def skip_common_prefix(iters: list):
0005     """Given a list of iterators, skips values until at least one iterator differs from the others. Returns the remaining iterators.
0006
0007     >>> [list(iter) for iter in skip_common_prefix(["hello"])]
0008     [['h', 'e', 'l', 'l', 'o']]
0009     >>> [list(iter) for iter in skip_common_prefix(["hello", "world!"])]
0010     [['h', 'e', 'l', 'l', 'o'], ['w', 'o', 'r', 'l', 'd', '!']]
0011     >>> [list(iter) for iter in skip_common_prefix([[3, 2, 1], [1, 2, 3, 4]])]
0012     [[3, 2, 1], [1, 2, 3, 4]]
0013     >>> [list(iter) for iter in skip_common_prefix([[1, 2, 3], [1, 2, 3, 4]])]
0014     [[], [4]]
0015     """
0016     # ensure that we have iterators, so that we can chain unconsumed tail in the end
0017     iters = list(map(iter, iters))
0018     if len(iters) == 0:
0019         raise ValueError("iters must not be empty")
0020     elif len(iters) == 1:
0021         tuple_iters = [zip(*iters)]
0022     else:
0023         tuple_iters = tee(
0024             dropwhile(lambda vals: all(val == vals[0] for val in vals), zip(*iters)),
0025             len(iters),
0026         )
0027     return list(starmap(
0028         lambda ix, tuple_iter: chain(map(lambda t: t[ix], tuple_iter), iters[ix]),
0029         enumerate(tuple_iters)
0030     ))