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