def char_collect_all(s, c):
    """
    Find all appearances of char in string
    :param s: haystack
    :param c: needle
    :return: list of indices
    """
    start = 0
    res = []
    clen = len(c)
    while True:
        start = s.find(c, start)
        if start == -1: break
        res.append(start)
        start += clen
    return res