def flatten(x):
"""flatten(sequence) -> list"""
result = []
for el in x:
# alternatively:
# if isinstance(el, (list, tuple)):
if (type(el) == list) or (type(el) == tuple):
result.extend(flatten(el))
else:
result.append(el)
return result
print(flatten([(1,2), "Python", ["a",[1,7]], 1, 1.3]))