面对对象之@classmethod、@staticmethod用法

@classmethod用法（修饰的函数，第一个参数cls默认是类名，调用方法：实例对象或类对象.方法）

class C_mthod(object):
    name = "f**k"
    def __init__(self,name):
        self.name = name
    @classmethod
    def t_mthod(cls):
        print("hello world",cls.name)

d = C_mthod("F**K")
C_mthod.t_mthod()

————————————————————
hello world f**k

@classmethod调用类静态方法，无法调用类继承方法

分享一个爬虫方法，仅供参考

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import random

import requests
from lxml import etree


class WanfangSpider(object):
    @classmethod
    def crawl_with_keyword(cls, keyword):
        url = 'http://s.wanfangdata.com.cn/Paper.aspx?q=' + keyword
        print url
        response = requests.get(url, cls.get_headers())
        if response.status_code == 200:
            return cls.get_info(response.text)
        else:
            return None

    @classmethod
    def get_headers(cls):
        user_agent = [
            'Mozilla / 5.0(compatible;MSIE9.0;Windows NT 6.1;Trident / 5.0',
            'Mozilla / 4.0(compatible;MSIE6.0;Windows NT 5.1',
            'Mozilla / 5.0(compatible;MSIE7.0;Windows NT 5.1',
            'Mozilla / 5.0(compatible;MSIE8.0;Windows NT 6.0',
            'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36'
        ]
        headers = {
            'User-Agent': random.choice(user_agent)
        }
        return headers

    @classmethod
    def get_info(cls, content):
        tree = etree.HTML(content)
        divs = tree.xpath('//*[@class="left-record"]')
        result = []
        for div in divs:
            a_dict = {}
            url = div.xpath('div/a[@class="title"]/@href')
            title = div.xpath('div/a[@class="title"]')[0].xpath('string(.)')
            subtitle = div.xpath('div[@class="record-subtitle"]')[0].xpath('string(.)')
            # print url, title, subtitle
            if not title:
                title = None

            if url:
                url = url[0]
            else:
                url = None

            if subtitle:
                subtitle = subtitle.strip()
            else:
                subtitle = None
            a_dict['url'] = url
            a_dict['title'] = title
            a_dict['subtitle'] = subtitle
            result.append(a_dict)
        return result


class It199Spider(object):
    @classmethod
    def crawl_with_keyword(cls, keyword):
        url = 'http://www.199it.com/archives/tag/' + keyword
        print url
        response = requests.get(url, cls.get_headers())
        if response.status_code == 200:
            return cls.get_info(response.text)
        else:
            return None

    @classmethod
    def get_headers(cls):
        user_agent = [
            'Mozilla / 5.0(compatible;MSIE9.0;Windows NT 6.1;Trident / 5.0',
            'Mozilla / 4.0(compatible;MSIE6.0;Windows NT 5.1',
            'Mozilla / 5.0(compatible;MSIE7.0;Windows NT 5.1',
            'Mozilla / 5.0(compatible;MSIE8.0;Windows NT 6.0',
            'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36'
        ]
        headers = {
            'User-Agent': random.choice(user_agent)
        }
        return headers

    @classmethod
    def get_info(cls, content):
        tree = etree.HTML(content)
        articles = tree.xpath('//article')
        result = []
        for article in articles:
            a_dict = {}

            # 提取正文
            img_url = article.xpath('div[@class="entry-list-left"]/div/a/img/@src')
            title = article.xpath('div[@class="entry-list-right"]/h2/a/text()')
            url = article.xpath('div[@class="entry-list-right"]/h2/a/@href')
            post_time = article.xpath('div[@class="entry-list-right"]/table/tr/td[2]/text()')
            tag = article.xpath('div[@class="entry-list-right"]/table/tr/td[4]/a/text()')
            summary = article.xpath('div[@class="entry-list-right"]/p[@class="post-excerpt"]/text()')
            print img_url, url, title, post_time, tag, summary

            # 构造字典
            a_dict['img_url'] = img_url[0] if img_url else None
            a_dict['title'] = title[0] if title else None
            a_dict['url'] = url[0] if url else None
            a_dict['post_time'] = post_time[0] if post_time else None
            a_dict['tag'] = tag[0] if tag else None
            a_dict['summary'] = summary[0] if summary else None
            result.append(a_dict)
        return result if len(result) < 10 else result[0: 10]

@staticmethod（不需要表示自身对象的self和自身类的cls参数，就跟使用函数一样。调用方法：实例对象或类对象.方法 ）

class A(object):
    bar = 1
    def foo(self):
        print('foo')

    @staticmethod
    def static_foo():
        print('static_foo')
        print(A.bar)

    @classmethod
    def class_foo(cls):
        print('class_foo')
        print(cls.bar)
        cls().foo()

A.static_foo()
A.class_foo()

——————————————————————
static_foo
1
class_foo
1
foo