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I have a project structured as such:
folder1
|
folder2
|
tests
I have __init__.py in each folder. When I am in the parent directory of folder1, I run iPython and do
from folder1.folder2.tests.test1 import main
main()
everything works fine. However when I run
python folder1/folder2/tests/test1.py
I get ImportError: No module named folder1.folder2.file1, where my import statement in test1 is
from folder1.folder2.file1 import class1
Confused about this - I am guessing it is a path issue but I don't understand what is wrong with my code (many similar setups in other folders) and why it still works in iPython and not python run as a script.
297
The Python "ImportError: cannot import name" occurs when we have circular imports (importing members between the same files). To solve the error, move the objects to a third file and import them from a central location in other files, or nest one of the imports in a function.
To run Python scripts with the python command, you need to open a command-line and type in the word python , or python3 if you have both versions, followed by the path to your script, just like this: $ python3 hello.py Hello World!
Using import * in python programs is considered a bad habit because this way you are polluting your namespace, the import * statement imports all the functions and classes into your own namespace, which may clash with the functions you define or functions of other libraries that you import.
The module search path (python 3 docu) is different with and without a script file:
(goes for both python and ipython)
$ python
Python 2.7.3 (default, Dec 18 2014, 19:10:20)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> print(sys.path)
['', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/pymodules/python2.7/gtk-2.0', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client', '/usr/lib/python2.7/dist-packages/ubuntuone-client', '/usr/lib/python2.7/dist-packages/ubuntuone-control-panel', '/usr/lib/python2.7/dist-packages/ubuntuone-couch', '/usr/lib/python2.7/dist-packages/ubuntuone-installer', '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol']
>>>
Note the first entry being an empty string. An empty string is a relative path equivalent to .. Relative paths in the module search path are relative to the current working dir of the interpreter process, so this is just the current working dir where you invoked the interpreter. (Which in your case happened to be the root of your project.)
$ echo 'import sys' > /tmp/pathtest.py
$ echo 'print(sys.path)' >> /tmp/pathtest.py
$ python /tmp/pathtest.py
['/tmp', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/pymodules/python2.7/gtk-2.0', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client', '/usr/lib/python2.7/dist-packages/ubuntuone-client', '/usr/lib/python2.7/dist-packages/ubuntuone-control-panel', '/usr/lib/python2.7/dist-packages/ubuntuone-couch', '/usr/lib/python2.7/dist-packages/ubuntuone-installer', '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol']
Note that here, the first entry is the absolute path of the directory containing the script file we passed as an argument.
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