python:两个配对列表的索引/分页

Question

假设我有两个这样的列表，它们必须成对表示:

cities = ['San Francisco', 'New York', 'Seattle', 'Portland', ]
states = ['CA', 'NY', 'WA', 'OR']

我有一个这样的函数:

def list(page):
    return "{0} -> {1} \n {2} -> {3} \n {4} -> {5} \n {6} -> {7}".format(keys[0], values[0], keys[1], values[1], keys[2], values[2], keys[3], values[3])

我希望能够使用一个整数(此处为 page)来索引这些对，一次显示三个。假设我有十对城市和州，1 它将显示前三个，2 后三个，等等。

伪装的，我想它看起来像这样:

def list(page):
    for page < 2:
        return first triplet
    for page < 3:
        return second triplet
    # etc.

但我认为可能有更好的方法，我想知道它会是什么样子。

Answer 1

设置:

cities = ['San Francisco', 'New York', 'Seattle', 'Portland', ]
states = ['CA', 'NY', 'WA', 'OR']

A function to split a generator into chunks :

from itertools import islice

def chunks(iterable, size=10):
    iterator = iter(iterable)
    for first in iterator:    # stops when iterator is depleted
        def chunk():          # construct generator for next chunk
            yield first       # yield element from for loop
            for more in islice(iterator, size - 1):
                yield more    # yield more elements from the iterator
        yield chunk()         # in outer generator, yield next chunk

这为您提供了一个生成给定大小块的生成器。放在一起:

>>> for chunk in chunks(zip(cities, states)):
...     for piece in chunk:
...             print('{}, {}'.format(*piece))
...
San Francisco, CA
New York, NY
Seattle, WA
Portland, OR

你也可以把它变成一个 list block ，如下所示:

>>> places = [list(chunk) for chunk in chunks(zip(cities, states), 3)]
>>> places[0]
[('San Francisco', 'CA'), ('New York', 'NY'), ('Seattle', 'WA')]

并打印给定的 block :

>>> print(*('{}, {}'.format(*place) for place in places[0]), sep='\n')
San Francisco, CA
New York, NY
Seattle, WA