Lib/test/test_unpack.py from CPython 3.8.2

CPython dev · youknowone · commit be8c71be24e4 · 2020-06-02T01:23:29.000+09:00
diff --git a/Lib/test/test_unpack.py b/Lib/test/test_unpack.py
@@ -0,0 +1,151 @@
+doctests = """
+
+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)
+
+"""
+
+__test__ = {'doctests' : doctests}
+
+def test_main(verbose=False):
+    from test import support
+    from test import test_unpack
+    support.run_doctest(test_unpack, verbose)
+
+if __name__ == "__main__":
+    test_main(verbose=True)
