如何在Python中使用类似next()的东西，但它允许我像在for循环中一样“单步”迭代？

Question

我有Python代码，可以让我迭代组合列表，我想跳过迭代并生成例如每100次迭代。我有一个 next() 函数，可以让组合暂时迭代 1，但我需要跳过它们。

我现在拥有的代码是：

def fastFunction(string, string1):

    try:
        return next(string)
    except StopIteration:
        return None

这个函数可以让我在迭代器被调用时生成下一个迭代。

class MyIterator:

    def __init__(self, hex_string, repeat, mapping_function=None, fixed_string=""):
        self.fixed_string = fixed_string  # Add a parameter for the fixed string
        combined_string = fixed_string+hex_string 
        self.repeat = repeat
        self.mapping_function = mapping_function
        if self.mapping_function:
            combined_string = self.mapping_function(combined_string)
        self.hex_string = combined_string
        self.fixed_part_length = len(fixed_string)
        self.combinations = itertools.product(self.hex_string, repeat=repeat - self.fixed_part_length)
        self.current = fastFunction(self.combinations, None)

    def __iter__(self):
        return self

    def modify_speed(self):
        pass

    def __next__(self):
        if self.current is not None:
            private_key =   self.fixed_string+ ''.join(self.current)    # Ensure the fixed string is part of the final key
            self.current = fastFunction(self.combinations, None)
            return private_key
        else:
            raise StopIteration

这就是迭代器，函数传入 self.current 等东西，让下一个组合出现。我想跳过迭代，这样我就可以立即生成每 100 次迭代。我怎样才能做到这一点？

Answer 1

要修改 MyIterator 类以跳过迭代并每 100 次迭代生成一次，您可以增强 fastFunction 以将迭代器推进指定的步数。

这是您的代码，稍作修改，进行了以下更改：

import itertools

def fastFunction(iterator, skip):
    try:
        for _ in range(skip + 1):
            next_value = next(iterator)
        return next_value
    except StopIteration:
        return None

class MyIterator:
    def __init__(self, hex_string, repeat, mapping_function=None, fixed_string="", skip=0):
        self.fixed_string = fixed_string  # Add a parameter for the fixed string
        combined_string = fixed_string + hex_string 
        self.repeat = repeat
        self.mapping_function = mapping_function
        if self.mapping_function:
            combined_string = self.mapping_function(combined_string)
        self.hex_string = combined_string
        self.fixed_part_length = len(fixed_string)
        self.combinations = itertools.product(self.hex_string, repeat=repeat - self.fixed_part_length)
        self.skip = skip
        self.current = fastFunction(self.combinations, self.skip)

    def __iter__(self):
        return self

    def modify_speed(self, new_skip):
        self.skip = new_skip

    def __next__(self):
        if self.current is not None:
            private_key = self.fixed_string + ''.join(self.current)  # Ensure the fixed string is part of the final key
            self.current = fastFunction(self.combinations, self.skip)
            return private_key
        else:
            raise StopIteration

# Example usage
iterator = MyIterator("0123456789ABCDEF", 4, fixed_string="fixed", skip=99)  # Skip 99 iterations to get every 100th
for _ in range(10):  # Get first 10 elements
    print(next(iterator))