flatten.py

flatten.py

def flatten1(l):
    s = [(l, 0)]
    x = [] 
    while s:
        d, i = s.pop()
        dlen  = len(d)
        while i < dlen:
            if isinstance(d[i], list):
                s.append((d, i+1))
                s.append((d[i], 0))
                break
            else:
                x.append(d[i])
            i += 1 
    return x 

def flatten2(l):
    s = [l]
    x = []
    while s:
        d = s.pop()
        for i in d:
            if isinstance(i, list):
                s.append(i)
            else:
                x.append(i)
    return x