python内置函数next()

next（）

def next(iterator, default=None): # real signature unknown; restored from __doc__
    """
    next(iterator[, default])
    
    Return the next item from the iterator. If default is given and the iterator
    is exhausted, it is returned instead of raising StopIteration.
    """
    pass

next（）函数接收的是一个迭代器，return的是该迭代器的next item。

next()函数自动调用文件第一行并返回下一行。这句话的意思是说第一次调用next（）函数会直接把第一行拿出来赋给左边，同时返回到下一行。第二次调用就把第二行拿出来，同时返回到下一行。

import csv
filename = 'sitka_weather_07-2014.csv'
with open(filename) as f:
    reader = csv.reader(f)
    header_row = next(reader)
    print(header_row)
    a=next(reader)
    print(a)
    b=next(reader)
    print(b)