On Aug 27, 2:43 pm, "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote: > 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
Hi Diez! I well understand the problem now, the fact is that unfortunately the external module is not mine and i doubt i can change it :-( Anyway as far as i'm concerned i've learned the lesson ! Thanks again and greetings, Nisp -- http://mail.python.org/mailman/listinfo/python-list
