Can anyone explain python's relative imports? [duplicate]
Solution 1:
You are importing from package "sub". start.py
is not itself in a package even if there is a __init__.py
present.
You would need to start your program from one directory over parent.py
:
./start.py
./pkg/__init__.py
./pkg/parent.py
./pkg/sub/__init__.py
./pkg/sub/relative.py
With start.py
:
import pkg.sub.relative
Now pkg is the top level package and your relative import should work.
If you want to stick with your current layout you can just use import parent
. Because you use start.py
to launch your interpreter, the directory where start.py
is located is in your python path. parent.py
lives there as a separate module.
You can also safely delete the top level __init__.py
, if you don't import anything into a script further up the directory tree.
Solution 2:
If you are going to call relative.py
directly and i.e. if you really want to import from a top level module you have to explicitly add it to the sys.path
list.
Here is how it should work:
# Add this line to the beginning of relative.py file
import sys
sys.path.append('..')
# Now you can do imports from one directory top cause it is in the sys.path
import parent
# And even like this:
from parent import Parent
If you think the above can cause some kind of inconsistency you can use this instead:
sys.path.append(sys.path[0] + "/..")
sys.path[0]
refers to the path that the entry point was ran from.
Solution 3:
Checking it out in python3:
python -V
Python 3.6.5
Example1:
.
├── parent.py
├── start.py
└── sub
└── relative.py
- start.py
import sub.relative
- parent.py
print('Hello from parent.py')
- sub/relative.py
from .. import parent
If we run it like this(just to make sure PYTHONPATH is empty):
PYTHONPATH='' python3 start.py
Output:
Traceback (most recent call last):
File "start.py", line 1, in <module>
import sub.relative
File "/python-import-examples/so-example-v1/sub/relative.py", line 1, in <module>
from .. import parent
ValueError: attempted relative import beyond top-level package
If we change import in sub/relative.py
- sub/relative.py
import parent
If we run it like this:
PYTHONPATH='' python3 start.py
Output:
Hello from parent.py
Example2:
.
├── parent.py
└── sub
├── relative.py
└── start.py
- parent.py
print('Hello from parent.py')
- sub/relative.py
print('Hello from relative.py')
- sub/start.py
import relative
from .. import parent
Run it like:
PYTHONPATH='' python3 sub/start.py
Output:
Hello from relative.py
Traceback (most recent call last):
File "sub/start.py", line 2, in <module>
from .. import parent
ValueError: attempted relative import beyond top-level package
If we change import in sub/start.py
:
- sub/start.py
import relative
import parent
Run it like:
PYTHONPATH='' python3 sub/start.py
Output:
Hello from relative.py
Traceback (most recent call last):
File "sub/start.py", line 3, in <module>
import parent
ModuleNotFoundError: No module named 'parent'
Run it like:
PYTHONPATH='.' python3 sub/start.py
Output:
Hello from relative.py
Hello from parent.py
Also it's better to use import from root folder, i.e.:
- sub/start.py
import sub.relative
import parent
Run it like:
PYTHONPATH='.' python3 sub/start.py
Output:
Hello from relative.py
Hello from parent.py