Google App Engine works a bit like CGI in that output to STDOUT goes to the browser. This breaks my normal "import pdb; pdb.set_trace()" trick. However, it's not hard to put STDOUT, etc. back so that you can use pdb in the way you normally would:
for attr in ('stdin', 'stdout', 'stderr'):
setattr(sys, attr, getattr(sys, '__%s__' % attr))
import pdb
pdb.set_trace()
12 comments:
Or use weberror's magical new pdb middleware! Well... I haven't tried it with appengine, so there's a decent chance it doesn't work there (but patches welcome).
Heh - I wondered about that today at the hackathon. I tried import pdb;pdb.set_trace() and got a weird error; now I guess i know why...
> Or use weberror's magical new pdb middleware! Well... I haven't tried it with appengine, so there's a decent chance it doesn't work there (but patches welcome).
Haha, as usual, you're way ahead of me.
You can also pass std{in,out} arguments to pdb.Pdb, like so:
def set_trace():
import pdb, sys
debugger = pdb.Pdb(stdin=sys.__stdin__,
stdout=sys.__stdout__)
debugger.set_trace(sys._getframe().f_back)
This messes with Google's sandbox less.
> This messes with Google's sandbox less.
Very helpful. Thanks!
I've tried the various methods mentioned here, but I always get errors displayed in the browser.
Using whit537's method I get this shown in the browser:
BdbQuit at /stop/37023745/
Request Method: GET
Request URL: http://localhost:8080/stop/37023745/
Exception Type: BdbQuit
Exception Value:
Exception Location: /System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/bdb.py in dispatch_call, line 80
It sounds like you're not successfully pointing stdout at the actual terminal. I'm surprised that my technique (in the main body of this blog post) doesn't work.
Actually, that does look like it works, I just can't work out how to attach to it, I'm running it through the Google App Engine Launcher on my mac if that makes any difference.
You need to figure out how to start the server from a shell. The start server script (whatever it's called) is on your Mac somewhere ;)
Turns out "dev_appserver.py" is on the defaultpath, probably set up by the installer, or the "Make Symlinks" option off the gui apps menu.
Go to your apps parent directory and run "dev_appserver.py yourappname"
I tried:
pdb.Pdb(stdin=getattr(sys,'__stdin__'),stdout=getattr(sys,'__stderr__')).set_trace(sys._getframe().f_back)
- the idea being leave stdout alone. Seems to work. I did not have any crap heading back toward the browser. Is there any best soln out there from someone who works on GAE (as a full time thing)?
> the idea being leave stdout alone. Seems to work.
Thanks.
> Is there any best soln out there from someone who works on GAE (as a full time thing)?
I have no clue.
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