mirror of https://github.com/python/cpython
Add all the examples from PEP 255, and a few email examples.
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Tim Peters
parent
1def351b45
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6ba5f79674
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@ -1,4 +1,4 @@
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simple_tests = """
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tutorial_tests = """
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Let's try a simple generator:
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>>> def f():
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@ -124,7 +124,188 @@ Generators can call other generators:
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"""
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__test__ = {"simple": simple_tests}
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# The examples from PEP 255.
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pep_tests = """
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Specification: Return
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Note that return isn't always equivalent to raising StopIteration: the
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difference lies in how enclosing try/except constructs are treated.
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For example,
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>>> def f1():
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... try:
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... return
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... except:
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... yield 1
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>>> print list(f1())
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[]
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because, as in any function, return simply exits, but
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>>> def f2():
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... try:
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... raise StopIteration
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... except:
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... yield 42
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>>> print list(f2())
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[42]
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because StopIteration is captured by a bare "except", as is any
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exception.
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Specification: Generators and Exception Propagation
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>>> def f():
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... return 1/0
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>>> def g():
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... yield f() # the zero division exception propagates
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... yield 42 # and we'll never get here
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>>> k = g()
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>>> k.next()
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Traceback (most recent call last):
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File "<stdin>", line 1, in ?
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File "<stdin>", line 2, in g
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File "<stdin>", line 2, in f
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ZeroDivisionError: integer division or modulo by zero
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>>> k.next() # and the generator cannot be resumed
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Traceback (most recent call last):
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File "<stdin>", line 1, in ?
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StopIteration
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>>>
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Specification: Try/Except/Finally
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>>> def f():
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... try:
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... yield 1
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... try:
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... yield 2
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... 1/0
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... yield 3 # never get here
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... except ZeroDivisionError:
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... yield 4
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... yield 5
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... raise
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... except:
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... yield 6
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... yield 7 # the "raise" above stops this
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... except:
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... yield 8
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... yield 9
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... try:
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... x = 12
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... finally:
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... yield 10
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... yield 11
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>>> print list(f())
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[1, 2, 4, 5, 8, 9, 10, 11]
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>>>
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Guido's binary tree example.
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>>> # A binary tree class.
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>>> class Tree:
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...
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... def __init__(self, label, left=None, right=None):
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... self.label = label
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... self.left = left
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... self.right = right
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...
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... def __repr__(self, level=0, indent=" "):
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... s = level*indent + `self.label`
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... if self.left:
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... s = s + "\\n" + self.left.__repr__(level+1, indent)
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... if self.right:
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... s = s + "\\n" + self.right.__repr__(level+1, indent)
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... return s
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...
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... def __iter__(self):
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... return inorder(self)
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>>> # Create a Tree from a list.
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>>> def tree(list):
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... n = len(list)
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... if n == 0:
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... return []
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... i = n / 2
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... return Tree(list[i], tree(list[:i]), tree(list[i+1:]))
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>>> # Show it off: create a tree.
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>>> t = tree("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
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>>> # A recursive generator that generates Tree leaves in in-order.
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>>> def inorder(t):
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... if t:
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... for x in inorder(t.left):
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... yield x
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... yield t.label
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... for x in inorder(t.right):
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... yield x
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>>> # Show it off: create a tree.
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... t = tree("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
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... # Print the nodes of the tree in in-order.
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... for x in t:
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... print x,
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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>>> # A non-recursive generator.
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>>> def inorder(node):
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... stack = []
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... while node:
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... while node.left:
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... stack.append(node)
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... node = node.left
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... yield node.label
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... while not node.right:
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... try:
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... node = stack.pop()
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... except IndexError:
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... return
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... yield node.label
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... node = node.right
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>>> # Exercise the non-recursive generator.
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>>> for x in t:
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... print x,
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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"""
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# A few examples from Iterator-List and Python-Dev email.
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email_tests = """
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The difference between yielding None and returning it.
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>>> def g():
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... for i in range(3):
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... yield None
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... yield None
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... return
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>>> list(g())
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[None, None, None, None]
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Ensure that explicitly raising StopIteration acts like any other exception
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in try/except, not like a return.
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>>> def g():
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... yield 1
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... try:
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... raise StopIteration
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... except:
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... yield 2
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... yield 3
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>>> list(g())
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[1, 2, 3]
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"""
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__test__ = {"tut": tutorial_tests,
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"pep": pep_tests,
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"zemail": email_tests}
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# Magic test name that regrtest.py invokes *after* importing this module.
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# This worms around a bootstrap problem.
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