code critique

Hey everyone, I finish this task with nice code. But I looking for inspection from you how to improve it.

I saw some peoples get crazy with binary that i didn't understand so much /=

L =  (8, 4, 2, 1)
def time_maker(var,what_is_it = 4):
    t = ""
    T = L[-(what_is_it):]
    for VAR in T:
        if VAR<=var:
            t+="-"
            var-=VAR
        else: t+="."
    return t

def checkio(data):
    data = [(x[:1], x[1:]) for x in data.split(':') ]
    T = []
    was_first = False
    for [a,b] in data:
        if b=="": b, a = a, '0'
        what_is_it = 3
        if not was_first :what_is_it, was_first = 2, True
        T.append(time_maker(int(a),what_is_it)+ " "+ time_maker(int(b)))

    return " : ".join(T)

Anyway, Thanks for the tips :-)