一、else语句
1、else 与if搭配,要么怎样,要么不怎样
if else 语句
2、else与while搭配,干完了怎么样,干不完就别想怎么样
count = 5
while count > 1:
if count%2 == 0:
print(count)
break #如果符合条件就打印,结束了整个程序,如果不符合一直循环,直至结束while,执行else语句
count -= 1
else:
print('错了')
运行:
>>>4
count = 5
while count > 1:
if count%6 == 0:
print(count)
break
count -= 1
else:
print('错了')
运行:
>>>错了
3、else与try搭配,没有问题,那就干吧
try:
int('123')
except ValueErrror :
print('出错了!')
else:
print('正常!')
运行:
>>> 正常!
二、with语句,会自动帮你考虑关闭文件的问题
with会自动处理文件的打开和关闭,如果中途出现异常会执行清理,确保文件的自动关闭
1、基本语法
try:
with open('data.txt','w') as f:
for each_line in f:
print(each_line)
2、with 处理多个项目的时候可以用逗号隔开组成一个语句
with A() as a,B() as b:
suite
3、实际例子,让with去考虑文件的打开与关闭
def file_compare(file1,file2) :
with open(file1) as f1,open(file2) as f2:
count = 0
differ = []
for line1 in f1:
line2 = f2.readline()
count += 1
if line1 != line2:
differ.append(count)
return differ
file1 = input('请输入需比较的第一个文件名:')
file2 = input('请输入需比较的第二个文件名:')
differ = file_compare(file1,file2)
if len(differ) == 0:
print('两个文件完全一样')
else:
print('两个文件共有【%d】处不一样:'% len(differ))
for each in differ:
print('第 %d 行不一样' % each)