1.常见的异常
# # NameError
# print(a)
# # IndexError: 索引错误
# li = [1,2,3,4]
# print(li[8])
# # KeyError
# d = dict(a=1, b=2)
# print(d['f'])
# # ZeroDivisionError: 除0错误
# print(10/(2-2))
# class Student(object):
# def __init__(self, name, age):
# self.name = name
# self.age = age
# def echo(self):
# print(self.name, self.age)
#
# # AttributeError: 对象没有该属性
# s1 = Student("westos", 10)
# # print(s1.scores)
# # s1.echo()
# # s1.echo1()
# # FileNotFoundError
# with open('/tmp/passwd9') as f:
# print(f.read(5))
# 总结: 在程序运行过程中影响程序正常运行的内容, 称为异常.
2._try_except语句
# python:try....except......finally......
# try:
# print(a)
# # 如果出现NameError时, 不报错, 只显示except语句里面执行的内容.
# except NameError:
# print("name error")
# print("hello")
# print("hello1 ")
# 捕获异常
try:
f = open("hello.txt", 'w')
f.write("这是一个测试文件")
# 注意: except语句不一定会执行, 只有在try语句中出现IOError报错时, 才会执行.
except IOError as e:
print(e)
# print("没有找到文件或者文件读取失败")
# 如果没有捕获到异常, 则执行else语句的内容
else:
print("文件内容写入成功")
# 无论是否捕获到异常, 都执行的语句.
finally:
f.close()
print("文件已经关闭")
#
# f = open("hello.txt", 'w')
# f.write("这是一个测试文件")
3.不指定异常类型的except使用
try:
f = open('hello.txt')
f.read()
except:
print("捕获所有的异常....")
else:
print("如果没有捕获到异常, 执行else语句")
finally:
f.close()
print("有异常或者没有异常都会执行")
4.捕获多个异常
# 异常处理
# assert(断言):
# NameError, KeyError
# try:
# d = dict(a=1, b=2)
# print(d['f']) # KeyError
# print(a) # NameError
# except KeyError as e:
# print(e)
# except NameError as e:
# print(e)
# else:
# print("没有产生异常")
# finally:
# print("无论是否产生异常的清理操作")
#
# print("new start")
try:
d = dict(a=1, b=2)
print(d['f']) # KeyError
print(a) # NameError
except (KeyError, NameError) as e:
print(e)
else:
print("没有产生异常")
finally:
print("无论是否产生异常的清理操作")
print("new start")
5.抛出异常_触发异常
class AgeError(BaseException):
pass
def get_age(age):
if 0 < age <= 200:
print(age)
else:
raise AgeError('invaild age')
get_age(1000)
get_age(100)
6.异常案例
while True:
try:
x = int(input("Please enter a number: "))
break
except ValueError:
print("Oops! That was no valid number. Try again")
7.抛出异常与继承
class B(Exception):
pass
class C(B):
pass
class D(C):
pass
for cls in [B, C, D]:
try:
raise cls()
except D:
print("D")
except C:
print("C")
except B:
print("B")
8.断言
def is_huiwen_num(num):
snum = str(num)
return snum == snum[::-1]
if __name__ == "__main__":
assert is_huiwen_num(100) == True, "error"
assert is_huiwen_num(101) == True
print("assert")
import unittest
9.logging模块
import logging
s = '0'
n = int(s)
# 配置日志的信息:
# 1). 日志级别: debug, info, warning, error, critical
# 2). level: 指日志级别为info及以上的日志信息会被记录到文件中;
# 3). format: 指定日志的格式, 可以去logging.Formatter查看参考信息
logging.basicConfig(filename="hello.log",level=logging.INFO,
format="%(asctime)s - %(filename)s[%(lineno)d] - %(levelname)s: %(message)s")
logging.debug("this is a debug info")
logging.info("this is a info")
logging.warning("这是一条警告信息")
# logging.info('n=%d' %n)
# print(10/n)
10.pdb_调试代码
import pdb
def pdb_run(args):
for i in range(args):
pdb.set_trace()
print(i)
return args
pdb.run("pdb_run(4)")