Some library seems to modify my sys.path, although I don't want ìt to be changed.
How can I find the python code line which alters sys.path?
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2 Answers
One of the first things imported is the sitecustomize and usercustomize modules; you could replace sys.path with a custom list implementation that records all changes being made.
First, find where to place a usercustomize or sitecustomize module; the site module can tell you where to place the first:
python -m site --user-site If that directory doesn't exist yet, create it and in it put a usercustomize.py with:
import sys class VerboseSysPath(list): def croak(self, action, args): frame = sys._getframe(2) print('sys.path.{}{} from {}:{}'.format( action, args, frame.f_code.co_filename, frame.f_lineno)) def insert(self, *args): self.croak('insert', args) return super().insert(*args) def append(self, *args): self.croak('append', args) return super().append(*args) def extend(self, *args): self.croak('extend', args) return super().extend(*args) def pop(self, *args): self.croak('pop', args) return super().pop(*args) def remove(self, *args): self.croak('remove', args) return super().remove(*args) def __delitem__(self, *args): self.croak('__delitem__', args) return super().__delitem__(*args) def __setitem__(self, *args): self.croak('__setitem__', args) return super().__setitem__(*args) sys.path = VerboseSysPath(sys.path) This now will complain about all attempts at altering the sys.path list.
Demo, with the above placed in either the site-packages/sitecustomize.py or `python -m site --user-site`/usercustomize.py modules:
$ cat test.py import sys sys.path.append('') $ bin/python test.py sys.path.append('',) from test.py:3 answered Feb 10, 2015 at 13:44
Martijn Pieters
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2 Comments
MarcinKonowalczyk
For anyone facing a similar problem: I couldn't trace the unexplained entries in
sys.path by adding this code to sitecustomize.py, so i've ended up temporarily hacking this into site.py itself and managed to solve the problem (.pth file leftover from a buggy installation). site.py is located in lib folder. Notably; if you're using a virtual environment, the core library does not come with, just lib/site-packages. You can find where your base installation is by looking at the first few entries in sys.path.
Martijn Pieters
@MarcinKonowalczyk: Ah, yes,
.pth files are processed before the *customize modules are imported. Note that .pth files in the per-user site-packages directory are loaded before those in the site directory, and any line that starts with import in such a file is executed, so you could use a .pth file instead of a usercustomize module to load the same sys.path instrumentation, and so not have to alter site.py.Starting python with python -S causes python not to load site.py, and so its default value is preserved from when python first starts up.
sys.paththen import module and check it again.