Python学习笔记——esle和with 语句

1. else与while组合

def showMaxFactor(num): count = num // 2 while count > 1: if num % count == 0: print('%d最大的约数是%d' % (num,count)) break count -= 1 # 如果循环中的语句全部执行完，没有中途跳出，则会执行else中的语句 else: print('%d是素数！' % num) num = int(input('请输入一个数：')) showMaxFactor(num)

请输入一个数：11 11是素数！

2. else与try组合

try: int('abc') except ValueError as reason: print('出错啦！' + str(reason)) else: print('没有任何异常！')

出错啦！invalid literal for int() with base 10: 'abc'

try: int('123') except ValueError as reason: print('出错啦！' + str(reason)) else: print('没有任何异常！')

没有任何异常！

3. with语句

# 用finally语句关闭文件 try: f = open('data.txt','w') for each_line in f: print(each_line) except OSError as reason: print('出错啦：' + str(reason)) finally: f.close() # 由于文件本来不存在，且未写入数据，所以文件不可读

出错啦：not readable

# 与上面的代码功能相同，用于关闭文件 try: with open('data.txt','w') as f: for each_line in f: print(each_line) except OSError as reason: print('出错啦：' + str(reason)) 

出错啦：not readable