nisp wrote: > On Aug 27, 9:56 am, Peter Otten <[EMAIL PROTECTED]> wrote: >> nisp wrote: >> > Hi all ! >> >> > I'm trying to capture stderr of an external module I use in my python >> > program. I'm doing this >> > by setting up a class in my module overwriting the stderr file object >> > method write. >> > The external module outputs to stderr this way: >> >> > from sys import std err >> >> > .... >> >> > print >> stderr, "Some text" >> >> > While in my module I use >> >> > import sys >> >> > ..... sys.stderr ... sys.stdout >> >> > Well, as long as I do not change in the external module those from/ >> > import statements to just >> >> > import sys >> >> > .... >> >> > print >> sys.stderr, "Some text" >> >> > I'm not able to capture its stderr and of course I would like not to >> > do this kind of change. >> > I've always been convinced of the equivalence of the two ways of using >> > the import statement >> > but it's clear I'm wrong :-( >> >> > Please, someone can tell me what's going on ? >> >> > Thanks in advance ! >> >> A practical approach to complement Diez' link to the explanation: >> >> Instead of modifying the external module you can either redirect stderr >> before you import the external module >> >> import sys >> sys.stderr = whatever >> import external >> >> or monkey-patch: >> >> import sys >> import external >> >> sys.stderr = external.sterr = whatever >> >> Peter > > Hi all ! > > Thanks first of all ! I read the interesting Diez's link but something > still remains to me unclear, on the other hand it's clear the my > problem is concentrated there and on symbols. > Here is what I'm trying to do > > HelloWorld.py: this is a real simplification of my external module > though still reflecting its structure (commented out is the version > that, let's say, works) > > from sys import stderr
This is your problem. You create a HelloWorld.stderr-alias to the object bound to sys.stderr. Rebinding the latter won't affect the former. That is precisely what the link I gave you explains. The short answer to the whole issue is: dont' use the from-import syntax until you really know what you are doing. Or not at all. Diez -- http://mail.python.org/mailman/listinfo/python-list
