Python中iter函数的具体使用

def iter(source, sentinel=None): # known special case of iter
    """
    iter(iterable) -> iterator
    iter(callable, sentinel) -> iterator
    
    Get an iterator from an object.  In the first form, the argument must
    supply its own iterator, or be a sequence.
    In the second form, the callable is called until it returns the sentinel.
    """
    pass

my_list = [1, 2, 3, 4, 5]
iterator = iter(my_list)

print(next(iterator))  # 输出：1
print(next(iterator))  # 输出：2

import random

def my_callable():
    return random.randint(1, 10)

iterator = iter(my_callable, 5)

print(next(iterator))  # 输出：1 到 10 之间的随机整数
print(next(iterator))  # 输出：1 到 10 之间的随机整数

print(next(iterator))  # 输出：3
print(next(iterator))  # 输出：7

def iter(source, sentinel=None):
    if sentinel is None:
        # Form 1: iter(iterable)
        return source.__iter__()
    else:
        # Form 2: iter(callable, sentinel)
        while True:
            value = source()
            if value == sentinel:
                break
            yield value