Python 3.3.2检查对象是否为文件类型 [英] Python 3.3.2 check that object is of type file
问题描述
我正在从Python 2.7移植到Python 3.3.2.在Python 2.7中,我曾经能够做类似assert(type(something) == file)
的操作,但是似乎在Python 3.3.2中这是错误的.如何在Python 3.3.2中做类似的事情?
I'm porting from Python 2.7 to Python 3.3.2. In Python 2.7, I used to be able to do something like assert(type(something) == file)
, but it seems that in Python 3.3.2 this is wrong. How do I do a similar thing in Python 3.3.2?
推荐答案
Python 3文件对象是 io
模块,针对该模块中的 ABC类进行测试:>
Python 3 file objects are part of the io
module, test against ABC classes in that module:
from io import IOBase
if isinstance(someobj, IOBase):
在Python 2中不要使用type(obj) == file
;您应该使用isinstance(obj, file)
代替.即使那样,您仍要测试功能; io
ABC允许您执行的操作; isinstance()
函数将为实现抽象方法的所有方法的任何对象返回True
.基类定义.
Don't use type(obj) == file
in Python 2; you'd use isinstance(obj, file)
instead. Even then, you would want to test for the capabilities; something the io
ABCs let you do; the isinstance()
function will return True
for any object that implements all the methods the Abstract Base Class defines.
演示:
>>> from io import IOBase
>>> fh = open('/tmp/demo', 'w')
>>> isinstance(fh, IOBase)
True
>>> isinstance(object(), IOBase)
False
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