# python实际编写过程中的问题整理 1. 类型转换与字符串拼接（+号）字符串替换 存在：int str float 等等 (没有string函数) ``` itemid = 125845 url = 'http://item.jd.com/' + str(itemid) + '.html' imgsrc = imgsrc.replace('/n5','/n1') ``` 2. 相等是两个等号 == id=123 print(id==123) //true 3. 判断文件（夹）是否存在,并创建 ``` if os.path.exists(filename) == True : //获取内容，内容为空则删除 if len(html) == 0: os.remove(filename) if os.path.exists(r'E:\pic')==False: os.mkdir(r'E:\pic') ``` 4. 读写文件 ``` f = open(filename,'rt',encoding='gbk') data = f.read() f.close() 或者用with with open(filename,'w',encoding='gbk') as f: f.write(data) ``` 5. 发送请求 ``` # -------------------------------------------------------- # requests 请求说明 # 请求方式有get/post/put/delete # 可以传入的参数有,url,headers,data,timeout,cookies,files等 # url = 'str' # headers = {'a':'1','b':'2'} # data = {'a':'1','b':'2'} # timeout = 3 #单位秒 # cookies = {'a':'1','b':'2'} # files = {'file': open('/path/a.xls', 'rb')} # ------------------------------------------------- # 请求结果后面可以跟content|text获取内容 + decode转码 # ------------------------- 示例如下： get_content = requests.get(url='httpxxxx',headers={'User-Agent':'xxx'},timeout=30).text.decode('utf-8) post_content = requests.post(url='httpxxxx',headers={'User-Agent':'xxx'},data={'a':1,'b':2},timeout=30).text.decode('utf-8) ``` 6. 正则用法 ``` import re ress = re.compile(r'url: "(.*)",id').search(txt) if ress: print (ress.group()) else: print ("No match!!") ress = re.search(r'url: "(.*)",id',txt).group() #返回所有匹配的字符 ress = re.search(r'url: "(.*)",id',txt).group(1) #返回正则括号中匹配的字符 ress = re.search(r'url: "(.*)",id',txt).span() #返回起始结束位置 ``` 默认search与match都是单行匹配，加flags=re.DOTALL实现多行匹配 `duty = re.search(r'<div class="bmsg job_msg inbox">(.*?)<div', content, flags=re.DOTALL)` 7. soup用法 ``` from bs4 import BeautifulSoup soup = BeautifulSoup(txt, 'lxml') soup.title.text soup.find('ul',class_="lh") soup.find_all('img') imgurl=[] for link in soup.find_all('img'): imgsrc = 'https:'+link.get('src') imgurl.append(imgsrc) ``` 8. 数据库连接 mongodb ``` pip install pymongo from pymongo import MongoClient conn = MongoClient('mongodb://lypeng:jobs89757Aa@119.29.52.50:27017') db = conn.local ``` 9. 线程与进程 10. 图形化gui编程之tkinter 11. 图像处理 12. 邮件发送 13.