def splice(alists, recycle = True):
"""
Accepts a list of nonempty lists or indexable objects in
argument alists (each element list may not be of the same
length) and a keyword argument recycle which
if true will reuse elements in lists of shorter length.
Any error will result in an empty list to be returned.
"""
try:
nlists = len(alists)
lens = [len(alist) for alist in alists]
if not recycle:
totlen = sum(lens)
else:
totlen = max(lens) * nlists
pos = [0] * nlists
R = [None] * totlen
i, j = 0, 0
while i < totlen:
if pos[j] < lens[j]:
R[i] = alists[j][pos[j]]
i += 1
pos[j] = pos[j] + 1
if recycle and pos[j] >= lens[j]:
pos[j] = 0
j = (j + 1) % nlists
return R
except:
return []
if __name__ == "__main__":
print splice([[1,2,3], ['a','b'], [4], [-1,-2,-3,-4]], recycle = False)
print splice([[1,2,3], ['a','b'], [4], [-1,-2,-3,-4]])
