Python_异常

1. 异常引入之ZeroDividionError

# _*_ coding:utf8 _*_
# 处理ZeroDivisionError

# print(5/0)
# print('zhi is my dream')

# 用 try-except 来处理异常
# try:
#     # 放要处理的语句
#     print(5/0)
# #     要处理的异常
# except ZeroDivisionError:
#     # 针对该异常提示什么或者做什么操作
#     print(" zero is not")
# # 正常执行该语句
# print(' this is my dream')

# 使用异常避免崩溃 else代码块
print("give me two number,and i will divison them")
print("Enter q is quit")
while True:
    first = input("please input your first number ")
    if first == 'q':
        break
    second = input('please input your second number')
    if second == 'q':
        break
    try:
        # 可能出现异常的放在try当中
        num = int(first)/int(second)
    except ZeroDivisionError:
            print("no no no no ")
    else:
        # 需要try中代码执行没有问题再去执行，就放在else中
        print(str(num))

2. FileNotFoundError

# 处理FileNotFoundError
file_name = 'alice.txt'
# with open(file_name) as file_object:
#     #  此处将会引发 FileNotFoundError
#     contents = file_object.read()

# 使用try-except
#     这个错误是 open()函数抛出的 所以try中要包含 open()

with open(file_name, 'w') as file_object:
    file_object.write(" i like you")

try:
    with open(file_name) as file_object:
        content = file_object.read()
        print(content)
except FileNotFoundError:
    print("文件没有找到")
else:
    # 以空格为分隔符，将读取到字符串分割，到列表中，赋值给变量contents
    contents = content.split()
    # 打印列表
    print(contents)
    # 获取到列表的长度
    print(len(contents))

# pass 语句：发生错误的时候，不会出现traceback和任何自定义的输入，（except中的）
# pass 还可以充当占位符，提醒你在程序的某个地方什么也没有做。