内置函数next()用于从迭代器返回下一个元素。通常该函数用在循环中。当它到达迭代器的末尾时，它会抛出一个错误。为了避免这种情况，我们可以指定默认值。
**next(iterator, default)** #where iterable can be list, tuple etc
下一个()参数:
接受两个参数。在这种情况下，迭代器可以是字符串、字节、元组、列表或范围，集合可以是字典、集合或冻结集合。
| 参数 | 描述 | 必需/可选 |
|---|---|---|
| 可迭代的 | 从迭代器中检索到下一项 | 需要 |
| 系统默认值 | 如果迭代器用尽，则返回该值 | 可选择的 |
下一个()返回值
如果它到达迭代器的末尾，并且没有指定默认值，它将引发 StopIteration 异常。
| 投入 | 返回值 | | 迭代程序 | 迭代器的下一个元素 |
Python 中next()方法的示例
示例 1:如何获取下一个项目
random = [5, 9, 'cat']
# converting the list to an iterator
random_iterator = iter(random)
print(random_iterator)
# Output: 5
print(next(random_iterator))
# Output: 9
print(next(random_iterator))
# Output: 'cat'
print(next(random_iterator))
# This will raise Error
# iterator is exhausted
print(next(random_iterator))
输出:
<list_iterator at="" object="">5
9
cat
Traceback (most recent call last):
File "python", line 18, in <module>StopIteration</module></list_iterator> 示例 2:将默认值传递给下一个()
random = [5, 9]
# converting the list to an iterator
random_iterator = iter(random)
# Output: 5
print(next(random_iterator, '-1'))
# Output: 9
print(next(random_iterator, '-1'))
# random_iterator is exhausted
# Output: '-1'
print(next(random_iterator, '-1'))
print(next(random_iterator, '-1'))
print(next(random_iterator, '-1'))
输出:
5
9
-1
-1
-1 示例 3:函数到达集合末尾时抛出一个错误
# Python `next()` function example
number = iter([256, 32, 82]) # Creating iterator
# Calling function
item = next(number)
# Displaying result
print(item)
# second item
item = next(number)
print(item)
# third item
item = next(number)
print(item)
# fourth item
item = next(number) # error, no item is present
print(item)
输出:
Traceback (most recent call last):
File "source_file.py", line 14, in
item = next(number)
StopIteration
256
32
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