イテレータ

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# イテレータの基本
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numbers = [1, 2, 3, 4, 5]
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iterator = iter(numbers)
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print(next(iterator))  # 1
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print(next(iterator))  # 2
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print(next(iterator))  # 3
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# イテレータプロトコル
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class MyIterator:
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    def __init__(self, data):
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        self.data = data
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        self.index = 0
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    def __iter__(self):
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        return self
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    def __next__(self):
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        if self.index < len(self.data):
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            result = self.data[self.index]
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            self.index += 1
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            return result
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        else:
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            raise StopIteration
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my_iter = MyIterator([1, 2, 3])
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for item in my_iter:
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    print(item)

1
# ジェネレータの基本
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def my_generator():
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    yield 1
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    yield 2
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    yield 3
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gen = my_generator()
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print(next(gen))  # 1
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print(next(gen))  # 2
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print(next(gen))  # 3
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# ジェネレータ式
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numbers = [1, 2, 3, 4, 5]
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squared = (x * x for x in numbers)
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for num in squared:
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    print(num)