Is There A Way To Redirect Stderr To File In Jupyter?

There was a redirect_output function in IPython.utils, and there was a %%capture magic function, but these are now gone, and this thread on the topic is now outdated. I'd like to d

Solution 1:

You could probably try replacing sys.stderr with some other file descriptor the same way as suggested here.

import sys
oldstderr = sys.stderr
sys.stderr = open('log.txt', 'w')
# do something
sys.stderr = oldstderr

Update: starting form Python 3.4, you should consuder using contextlib.redirect_stdout() instead, like this:

f = io.StringIO()
withredirect_stdout(f):
    print('a')
s = f.getvalue()

Solution 2:

@Ben, just replacing sys.stderr did not work, and the full flush logic suggested in the post was necessary. But thank you for the pointer as it finally gave me a working version:

import sys
oldstderr = sys.stderr
sys.stderr = open('log.txt', 'w')
classflushfile():
    def__init__(self, f):
        self.f = f
    def__getattr__(self,name): 
        returnobject.__getattribute__(self.f, name)
    defwrite(self, x):
        self.f.write(x)
        self.f.flush()
    defflush(self):
        self.f.flush()
sys.sterr = flushfile(sys.stderr)
from __future__ import print_function
# some long running function here, e.g. for i inrange(1000000):
    print('hello!', file=sys.stderr)
sys.stderr = oldstderr

It would have been nice if Jupyter kept the redirect_output() function and/or the %%capture magic.