Python：如何从导入的模块中调用类方法？ “自我”论证问题

Question

我有 2 个文件。我知道如何调用函数，但无法理解如何正确地从以“self”作为第一个参数的导入模块调用方法。

我收到了这个错误：

TypeError: prepare() 缺少 1 个必需的位置参数：'url'

cinemas.py    

import requests
from lxml.html import fromstring

class cinemas_info():

    def __init__(self, url):
        self.basic_cinemas_info(url)

    def prepare(self, url):


        url = requests.get(url)
        tree = fromstring(url.text)
        tree.make_links_absolute(url.url)
        return tree

    def basic_cinemas_info(self, url):


        tree = self.prepare(url)

        for city in tree.xpath(".//div[@class='city-caption']"):
            city1 = city.xpath("text()")[0]
            for cinema in city.xpath("following-sibling::*[1]/li/a"):
                name1 = cinema.xpath("text()")[0]
                detailed_url = cinema.xpath("@href")[0]
                print (city1.strip(), name1.strip(), ':')
                self.detailed_cinemas_info(detailed_url)
                self.detailed_cinemas_films(detailed_url)

    def detailed_cinemas_info(self, url):


        tree = self.prepare(url)

        for street in tree.xpath(".//div[@class='address']"):
            street1 = street.xpath("text()")[0]
            for phone in tree.xpath(".//div[@class='phone']"):
                phone1 = phone.xpath("text()")[0]
                for website in tree.xpath(".//div[@class='website']/a"):
                    website1 = website.xpath("@href")[0]
                    print ('\t', street1.strip(), phone1.strip(), website1.strip())

    def detailed_cinemas_films(self, url):


        showtimes_tab_url = '/showtimes/#!=&cinema-section=%2Fshowtimes%2F'
        tree = self.prepare(url + showtimes_tab_url)

        for film in tree.xpath('//div[@class="content"]'):
            film_name = film.xpath('.//a[@class="navi"]/text()')[0]
            for dates in film.xpath('.//li[contains(@class,"showtimes-day sdt")]'):
                film_dates = dates.xpath('.//div[@class="date"]/text()')[0]
                for times in dates.xpath('.//ul[@class="showtimes-day-block"]/li'):
                    film_times = times.xpath('a/text()')

                    if len(film_times) == 0:
                        film_times = None

                    is_3d = times.find('span')
                    if film_times is not None:
                        if is_3d is not None:
                            print(film_dates, film_name, film_times[0], '3D')
                        else:
                            print(film_dates, film_name, film_times[0])

if __name__ == "__main__":
    cinemas_info('http://vkino.com.ua/cinema/#!=')

.

#films.py

import requests
from cinemas import cinemas_info

def films_list():
    url = 'http://vkino.com.ua/afisha#!='
    tree = cinemas_info.prepare(url) #  <<<----Here is my call

    for films in tree.xpath('//*[@id="content"]/div/div[1]/ul[2]/li'):
        film_name = films.xpath('.//div[@class="title"]/a/text()')[0]
        film_url = films.xpath('.//div[@class="title"]/a/@href')[0]
        print(film_name, film_url)

if __name__ == "__main__":
    films_list()

我知道我可以将“def prepare”移出类并删除“self”参数，但我想知道，在类中调用“def prepare”的正确方法是什么。

Answer 1

由于prepare 的定义中包含self，因此您可以在cinemas_info 的实例上调用此方法，或者将其实例和url 传递给prepare()。

所以你只需要创建一个cinemas_info 类的实例，Python 会自己将该实例传递给prepare()。您只需传递url。

#films.py

import requests
from cinemas import cinemas_info

def films_list():
    url = 'http://vkino.com.ua/afisha#!='
    c_info = cinemas_info(url) # created an instance of cinemas_info
    tree = c_info.prepare(url) # can now call prepare() on this instance

    for films in tree.xpath('//*[@id="content"]/div/div[1]/ul[2]/li'):
        film_name = films.xpath('.//div[@class="title"]/a/text()')[0]
        film_url = films.xpath('.//div[@class="title"]/a/@href')[0]
        print(film_name, film_url)

if __name__ == "__main__":
    films_list()

Answer 2

from cinemas import cinemas_info

您在此处导入类定义。现在下一行：

cinemas_info.prepare(url)

你在这个类定义上调用prepare。你想要的是先实例化类，然后在类的instance上调用prepare()。

ci = cinemas_info(url)
ci.prepare(url)  # this works

编辑：当您在 instance 上调用方法时，Python 会自动填充 self 变量作为对该对象实例的引用，因此您只需将一个参数传递给def prepare(self, url)。