人言落日是天涯，望极天涯不见家 wrote:
> I wanna print the log to both the screen and file, so I simulatered a
> 'tee'
>
> class Tee(file):
>
> def __init__(self, name, mode):
> file.__init__(self, name, mode)
> self.stdout = sys.stdout
> sys.stdout = self
>
> def __del__(self):
> sys.stdout = self.stdout
> self.close()
>
> def write(self, data):
> file.write(self, data)
> self.stdout.write(data)
>
> Tee('logfile', 'w')
> print >>sys.stdout, 'abcdefg'
>
> I found that it only output to the file, nothing to screen. Why?
> It seems the 'write' function was not called when I *print* something.
There are places in the C code of Python that do the equivalent of
if isinstance(file_like_object, file):
file.write(file_like_object, text)
else:
file_like_object.write(text)
Therefore you can't safely inherit from file. The workaround is to make your
own file-like object; yours would become
class Tee(object):
def __init__(self, name, mode):
self.file = open(name, mode)
self.stdout = sys.stdout
sys.stdout = self
def __del__(self):
sys.stdout = self.stdout
self.file.close()
def write(self, data):
self.file.write(data)
self.stdout.write(data)
Peter
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