B u9a @s,dZdeiZd ddZedkr(edddS) a Unpack tuple >>> t = (1, 2, 3) >>> a, b, c = t >>> a == 1 and b == 2 and c == 3 True Unpack list >>> l = [4, 5, 6] >>> a, b, c = l >>> a == 4 and b == 5 and c == 6 True Unpack implied tuple >>> a, b, c = 7, 8, 9 >>> a == 7 and b == 8 and c == 9 True Unpack string... fun! >>> a, b, c = 'one' >>> a == 'o' and b == 'n' and c == 'e' True Unpack generic sequence >>> class Seq: ... def __getitem__(self, i): ... if i >= 0 and i < 3: return i ... raise IndexError ... >>> a, b, c = Seq() >>> a == 0 and b == 1 and c == 2 True Single element unpacking, with extra syntax >>> st = (99,) >>> sl = [100] >>> a, = st >>> a 99 >>> b, = sl >>> b 100 Now for some failures Unpacking non-sequence >>> a, b, c = 7 Traceback (most recent call last): ... TypeError: cannot unpack non-iterable int object Unpacking tuple of wrong size >>> a, b = t Traceback (most recent call last): ... ValueError: too many values to unpack (expected 2) Unpacking tuple of wrong size >>> a, b = l Traceback (most recent call last): ... ValueError: too many values to unpack (expected 2) Unpacking sequence too short >>> a, b, c, d = Seq() Traceback (most recent call last): ... ValueError: not enough values to unpack (expected 4, got 3) Unpacking sequence too long >>> a, b = Seq() Traceback (most recent call last): ... ValueError: too many values to unpack (expected 2) Unpacking a sequence where the test for too long raises a different kind of error >>> class BozoError(Exception): ... pass ... >>> class BadSeq: ... def __getitem__(self, i): ... if i >= 0 and i < 3: ... return i ... elif i == 3: ... raise BozoError ... else: ... raise IndexError ... Trigger code while not expecting an IndexError (unpack sequence too long, wrong error) >>> a, b, c, d, e = BadSeq() Traceback (most recent call last): ... test.test_unpack.BozoError Trigger code while expecting an IndexError (unpack sequence too short, wrong error) >>> a, b, c = BadSeq() Traceback (most recent call last): ... test.test_unpack.BozoError Allow unpacking empty iterables >>> () = [] >>> [] = () >>> [] = [] >>> () = () Unpacking non-iterables should raise TypeError >>> () = 42 Traceback (most recent call last): ... TypeError: cannot unpack non-iterable int object Unpacking to an empty iterable should raise ValueError >>> () = [42] Traceback (most recent call last): ... ValueError: too many values to unpack (expected 0) doctestsFcCs(ddlm}ddlm}|||dS)N)support) test_unpack)ZtestrrZ run_doctest)verboserrr!/usr/lib/python3.7/test_unpack.py test_mains  r__main__T)rN)F)rZ__test__r__name__rrrrs