流畅的 Python 第二版（GPT 重译）（九）(3)

>>> list(itertools.product('ABC', range(2)))  # ①
[('A', 0), ('A', 1), ('B', 0), ('B', 1), ('C', 0), ('C', 1)] >>> suits = 'spades hearts diamonds clubs'.split()
>>> list(itertools.product('AK', suits))  # ②
[('A', 'spades'), ('A', 'hearts'), ('A', 'diamonds'), ('A', 'clubs'), ('K', 'spades'), ('K', 'hearts'), ('K', 'diamonds'), ('K', 'clubs')] >>> list(itertools.product('ABC'))  # ③
[('A',), ('B',), ('C',)] >>> list(itertools.product('ABC', repeat=2))  # ④
[('A', 'A'), ('A', 'B'), ('A', 'C'), ('B', 'A'), ('B', 'B'), ('B', 'C'), ('C', 'A'), ('C', 'B'), ('C', 'C')] >>> list(itertools.product(range(2), repeat=3))
[(0, 0, 0), (0, 0, 1), (0, 1, 0), (0, 1, 1), (1, 0, 0), (1, 0, 1), (1, 1, 0), (1, 1, 1)] >>> rows = itertools.product('AB', range(2), repeat=2)
>>> for row in rows: print(row)
...
('A', 0, 'A', 0) ('A', 0, 'A', 1) ('A', 0, 'B', 0) ('A', 0, 'B', 1) ('A', 1, 'A', 0) ('A', 1, 'A', 1) ('A', 1, 'B', 0) ('A', 1, 'B', 1) ('B', 0, 'A', 0) ('B', 0, 'A', 1) ('B', 0, 'B', 0) ('B', 0, 'B', 1) ('B', 1, 'A', 0) ('B', 1, 'A', 1) ('B', 1, 'B', 0) ('B', 1, 'B', 1)

>>> ct = itertools.count()  # ①
>>> next(ct)  # ②
0 >>> next(ct), next(ct), next(ct)  # ③
(1, 2, 3) >>> list(itertools.islice(itertools.count(1, .3), 3))  # ④
[1, 1.3, 1.6] >>> cy = itertools.cycle('ABC')  # ⑤
>>> next(cy)
'A' >>> list(itertools.islice(cy, 7))  # ⑥
['B', 'C', 'A', 'B', 'C', 'A', 'B'] >>> list(itertools.pairwise(range(7)))  # ⑦
[(0, 1), (1, 2), (2, 3), (3, 4), (4, 5), (5, 6)] >>> rp = itertools.repeat(7)  # ⑧
>>> next(rp), next(rp)
(7, 7) >>> list(itertools.repeat(8, 4))  # ⑨
[8, 8, 8, 8] >>> list(map(operator.mul, range(11), itertools.repeat(5)))  # ⑩
[0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50]

>>> list(itertools.combinations('ABC', 2))  # ①
[('A', 'B'), ('A', 'C'), ('B', 'C')] >>> list(itertools.combinations_with_replacement('ABC', 2))  # ②
[('A', 'A'), ('A', 'B'), ('A', 'C'), ('B', 'B'), ('B', 'C'), ('C', 'C')] >>> list(itertools.permutations('ABC', 2))  # ③
[('A', 'B'), ('A', 'C'), ('B', 'A'), ('B', 'C'), ('C', 'A'), ('C', 'B')] >>> list(itertools.product('ABC', repeat=2))  # ④
[('A', 'A'), ('A', 'B'), ('A', 'C'), ('B', 'A'), ('B', 'B'), ('B', 'C'), ('C', 'A'), ('C', 'B'), ('C', 'C')]

>>> list(itertools.groupby('LLLLAAGGG'))  # ①
[('L', <itertools._grouper object at 0x102227cc0>), ('A', <itertools._grouper object at 0x102227b38>), ('G', <itertools._grouper object at 0x102227b70>)] >>> for char, group in itertools.groupby('LLLLAAAGG'):  # ②
...     print(char, '->', list(group))
...
L -> ['L', 'L', 'L', 'L'] A -> ['A', 'A',] G -> ['G', 'G', 'G'] >>> animals = ['duck', 'eagle', 'rat', 'giraffe', 'bear',
...            'bat', 'dolphin', 'shark', 'lion']
>>> animals.sort(key=len)  # ③
>>> animals
['rat', 'bat', 'duck', 'bear', 'lion', 'eagle', 'shark', 'giraffe', 'dolphin'] >>> for length, group in itertools.groupby(animals, len):  # ④
...     print(length, '->', list(group))
...
3 -> ['rat', 'bat'] 4 -> ['duck', 'bear', 'lion'] 5 -> ['eagle', 'shark'] 7 -> ['giraffe', 'dolphin'] >>> for length, group in itertools.groupby(reversed(animals), len): # ⑤
...     print(length, '->', list(group))
...
7 -> ['dolphin', 'giraffe'] 5 -> ['shark', 'eagle'] 4 -> ['lion', 'bear', 'duck'] 3 -> ['bat', 'rat'] >>>

>>> list(itertools.tee('ABC'))
[<itertools._tee object at 0x10222abc8>, <itertools._tee object at 0x10222ac08>]
>>> g1, g2 = itertools.tee('ABC')
>>> next(g1)
'A'
>>> next(g2)
'A'
>>> next(g2)
'B'
>>> list(g1)
['B', 'C']
>>> list(g2)
['C']
>>> list(zip(*itertools.tee('ABC')))
[('A', 'A'), ('B', 'B'), ('C', 'C')]

>>> all([1, 2, 3])
True >>> all([1, 0, 3])
False >>> all([])
True >>> any([1, 2, 3])
True >>> any([1, 0, 3])
True >>> any([0, 0.0])
False >>> any([])
False >>> g = (n for n in [0, 0.0, 7, 8])
>>> any(g)  # ①
True >>> next(g)  # ②
8

>>> def sub_gen():
...     yield 1.1
...     yield 1.2
...
>>> def gen():
...     yield 1
...     for i in sub_gen():
...         yield i
...     yield 2
...
>>> for x in gen():
...     print(x)
...
1
1.1
1.2
2

>>> def sub_gen():
...     yield 1.1
...     yield 1.2
...
>>> def gen():
...     yield 1
...     yield from sub_gen()
...     yield 2
...
>>> for x in gen():
...     print(x)
...
1
1.1
1.2
2

>>> def sub_gen():
...     yield 1.1
...     yield 1.2
...     return 'Done!'
...
>>> def gen():
...     yield 1
...     result = yield from sub_gen()
...     print('<--', result)
...     yield 2
...
>>> for x in gen():
...     print(x)
...
1
1.1
1.2
<-- Done!
2

>>> def chain(*iterables):
...     for it in iterables:
...         for i in it:
...             yield i
...
>>> s = 'ABC'
>>> r = range(3)
>>> list(chain(s, r))
['A', 'B', 'C', 0, 1, 2]

>>> def chain(*iterables):
...     for i in iterables:
...         yield from i
...
>>> list(chain(s, t))
['A', 'B', 'C', 0, 1, 2]

def tree(cls):
    yield cls.__name__
def display(cls):
    for cls_name in tree(cls):
        print(cls_name)
if __name__ == '__main__':
    display(BaseException)

BaseException
• 1

$ python3 tree.py
BaseException
    Exception
    GeneratorExit
    SystemExit
    KeyboardInterrupt

def tree(cls):
    yield cls.__name__, 0                        # ①
    for sub_cls in cls.__subclasses__():         # ②
        yield sub_cls.__name__, 1                # ③
def display(cls):
    for cls_name, level in tree(cls):
        indent = ' ' * 4 * level                 # ④
        print(f'{indent}{cls_name}')
if __name__ == '__main__':
    display(BaseException)

def tree(cls):
    yield cls.__name__, 0
    yield from sub_tree(cls)              # ①
def sub_tree(cls):
    for sub_cls in cls.__subclasses__():
        yield sub_cls.__name__, 1         # ②
def display(cls):
    for cls_name, level in tree(cls):     # ③
        indent = ' ' * 4 * level
        print(f'{indent}{cls_name}')
if __name__ == '__main__':
    display(BaseException)

def tree(cls):
    yield cls.__name__, 0
    yield from sub_tree(cls)
def sub_tree(cls):
    for sub_cls in cls.__subclasses__():
        yield sub_cls.__name__, 1
        for sub_sub_cls in sub_cls.__subclasses__():
            yield sub_sub_cls.__name__, 2
def display(cls):
    for cls_name, level in tree(cls):
        indent = ' ' * 4 * level
        print(f'{indent}{cls_name}')
if __name__ == '__main__':
    display(BaseException)

$ python3 tree.py
BaseException
    Exception
        TypeError
        StopAsyncIteration
        StopIteration
        ImportError
        OSError
        EOFError
        RuntimeError
        NameError
        AttributeError
        SyntaxError
        LookupError
        ValueError
        AssertionError
        ArithmeticError
        SystemError
        ReferenceError
        MemoryError
        BufferError
        Warning
    GeneratorExit
    SystemExit
    KeyboardInterrupt