python - module level code run twice when patching -

python - module level code run twice when patching -

consider next simple code:

test_code.py

def f(): homecoming 'unpatched' import patch_stuff patch_stuff.patch_it_up() print f()

patch_stuff.py

from mock import patch def patch_it_up(): p = patch('test_code.f') m = p.start() m.return_value = 'patched'

i expect output of running python test_code.py be

patched

however output is:

unpatched patched

how come?

there 2 problems in code. first, test_code.py file called twice - first when phone call it, , 1 time again when mock imports purpose of creating patch. should alter follows:

def f(): homecoming 'unpatched' import patch_stuff if __name__ == "__main__": patch_stuff.patch_it_up() print f()

this print 'unpatched' string. leads sec thing: the documentation suggests not how patchers work. when phone call start method returns patched object used. expected output can achieved next modifications:

patch_stuff.py

from mock import patch def patch_it_up(): p = patch('test_code.f') m = p.start() m.return_value = 'patched' homecoming m

test_code.py

def f(): homecoming 'unpatched' import patch_stuff if __name__ == "__main__": m = patch_stuff.patch_it_up() print m()

this print expected 'patched' string.

this makes scenario not practical, examples in documentation show possibility of modifying modules imported in current context. e.g., work:

from mock import patch def patch_it_up(): import test_code p = patch('test_code.f') m = p.start() m.return_value = 'patched' print "inside patch_it_up:", test_code.f()

python mocking python-mock patching