open()和with open() as的区别

2020-03-18  20:37:55

open()和with open() as的区别

1 file = open("test.txt","r")
2 for line in file.readlines():
3     print line
4 file.close()

这样直接打开文件，如果出现异常，如读取过程中文件不存在或异常，则直接出现错误，close方法无法执行，文件无法关闭

1 with open("test.txt","r") as file:
2     for line in file.readlines():
3         print line

二者的运行的结果是相同的，但是with open（）as会在语句结束自动关闭文件，即便出现异常。

1 file= open("test.txt","r")
2 try:
3     for line in file.readlines():
4         print line
5 except:
6     print "error"
7 finally:
8     file.close()

with open() as语句作用效果相当于上面的try-except-finally