异常值的处理:try & 爬虫初识

---------------------------异常值处理-------------------------

异常值处理：防止程序奔溃

• #常见的用法
  try:   
      val = input('请输入数字：')
      num = int(val)
  except Exception as e: #Exception固定格式：捕获所有类型的异常
      print('操作异常') #如果程序报错，执行如下内容
          
  # 也可用于函数        
  def func(a):
      try:
          a.strip()
      except Exception as e:
          print('处理失败')
      return 123
  v  = func([11,22,33])
  print(v)
      
  

#捕获单个异常
try:
    print("----text-----1----")
    f = open("123.txt","r")
    print("-----test------2---")

    print(num)
except(NameError,IOError)as result:#IOError:输入输出错误，如果两个错误都有的话，并列加括号。
    print("产生错误了")
    print(result)#产生错误的提示信息

异常练习题

import time
try:
    f = open("123.tet","r")
    try:
        while True:
            content = f.readline()
            if len(content) == 0:
                break
            time.sleep(2)
            print(content)
    finally:#不论有没有异常finally一定会被执行，保证文件异常与否都会被关闭
        f.close()
        print("文件关闭")
except Exception as result:
    print("发生异常")

爬虫的应用

import requests
def func1(url_list):
result = []
for url in url_list:
try:
response = requests.get(url)
result.append(response.text)
except Exception as e:
pass
return result
func1(['http://www.baidu.com','http://www.google.com'])