Python 3.5+: How to dynamically import a module given the full file path (in the presence of implicit sibling imports)?
The easiest solution I could come up with is to temporarily modify sys.path
in the function doing the import:
from contextlib import contextmanager
@contextmanager
def add_to_path(p):
import sys
old_path = sys.path
sys.path = sys.path[:]
sys.path.insert(0, p)
try:
yield
finally:
sys.path = old_path
def path_import(absolute_path):
'''implementation taken from https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly'''
with add_to_path(os.path.dirname(absolute_path)):
spec = importlib.util.spec_from_file_location(absolute_path, absolute_path)
module = importlib.util.module_from_spec(spec)
spec.loader.exec_module(module)
return module
This should not cause any problems unless you do imports in another thread concurrently. Otherwise, since sys.path
is restored to its previous state, there should be no unwanted side effects.
Edit:
I realize that my answer is somewhat unsatisfactory but, digging into the code reveals that, the line spec.loader.exec_module(module)
basically results in exec(spec.loader.get_code(module.__name__),module.__dict__)
getting called. Here spec.loader.get_code(module.__name__)
is simply the code contained in lib.py.
Thus a better answer to the question would have to find a way to make the import
statement behave differently by simply injecting one or more global variables through the second argument of the exec-statement. However, "whatever you do to make the import machinery look in that file's folder, it'll have to linger beyond the duration of the initial import, since functions from that file might perform further imports when you call them", as stated by @user2357112 in the question comments.
Unfortunately the only way to change the behavior of the import
statement seems to be to change sys.path
or in a package __path__
. module.__dict__
already contains __path__
so that doesn't seem to work which leaves sys.path
(Or trying to figure out why exec does not treat the code as a package even though it has __path__
and __package__
... - But I don't know where to start - Maybe it has something to do with having no __init__.py
file).
Furthermore this issue does not seem to be specific to importlib
but rather a general problem with sibling imports.
Edit2: If you don't want the module to end up in sys.modules
the following should work (Note that any modules added to sys.modules
during the import are removed):
from contextlib import contextmanager
@contextmanager
def add_to_path(p):
import sys
old_path = sys.path
old_modules = sys.modules
sys.modules = old_modules.copy()
sys.path = sys.path[:]
sys.path.insert(0, p)
try:
yield
finally:
sys.path = old_path
sys.modules = old_modules
add to the PYTHONPATH
environment variable the path your application is on
Augment the default search path for module files. The format is the same as the shell’s PATH: one or more directory pathnames separated by os.pathsep (e.g. colons on Unix or semicolons on Windows). Non-existent directories are silently ignored.
on bash its like this:
export PYTHONPATH="./folder/:${PYTHONPATH}"
or run directly:
PYTHONPATH="./folder/:${PYTHONPATH}" python directory/app.py