“ImportError: No module named” when trying to run Python script

Question

I'm trying to run a script that launches, amongst other things, a python script. I get a ImportError: No module named ..., however, if I launch ipython and import the same module in the same way through the interpreter, the module is accepted.

What's going on, and how can I fix it? I've tried to understand how python uses PYTHONPATH but I'm thoroughly confused. Any help would greatly appreciated.

Answer 1

This issue arises due to the ways in which the command line IPython interpreter uses your current path vs. the way a separate process does (be it an IPython notebook, external process, etc). IPython will look for modules to import that are not only found in your sys.path, but also on your current working directory. When starting an interpreter from the command line, the current directory you're operating in is the same one you started ipython in. If you run

import os
os.getcwd() 

you'll see this is true.

However, let's say you're using an ipython notebook, run os.getcwd() and your current working directory is instead the folder in which you told the notebook to operate from in your ipython_notebook_config.py file (typically using the c.NotebookManager.notebook_dir setting).

The solution is to provide the python interpreter with the path-to-your-module. The simplest solution is to append that path to your sys.path list. In your notebook, first try:

import sys
sys.path.append('my/path/to/module/folder')

import module-of-interest

If that doesn't work, you've got a different problem on your hands unrelated to path-to-import and you should provide more info about your problem.

The better (and more permanent) way to solve this is to set your PYTHONPATH, which provides the interpreter with additional directories look in for python packages/modules. Editing or setting the PYTHONPATH as a global var is os dependent, and is discussed in detail here for Unix or Windows.

Answer 2

Just create an empty python file with the name __init__.py under the folder which showing error, while you running the python project.

Answer 3

Make sure they are both using the same interpreter. This happened to me on Ubuntu:

$ ipython3 -c 'import sys; print(sys.version)'
3.4.2 (default, Jun 19 2015, 11:34:49) \n[GCC 4.9.1]

$ python3 -c 'import sys; print(sys.version)'
3.3.0 (default, Nov 27 2012, 12:11:06) \n[GCC 4.6.3]

And sys.path was different between the two interpreters. To fix it, I removed Python 3.3.

Answer 4

Doing sys.path.append('my-path-to-module-folder') will work, but to avoid having to do this in IPython every time you want to use the module, you can add export PYTHONPATH="my-path-to-module-folder:$PYTHONPATH" to your ~/.bash_profile file.

Answer 5

The main reason is the sys.paths of Python and IPython are different.

Please refer to lucypark link, the solution works in my case. It happen when install opencv by

conda install opencv

And got import error in iPython, There are three steps to solve this issue:

import cv2
ImportError: ...

1. Check path in Python and iPython with following command

import sys
sys.path

You will find different result from Python and Jupyter. Second step, just use sys.path.append to fix the missed path by try-and-error.

2. Temporary solution

In iPython:

import sys
sys.path.append('/home/osboxes/miniconda2/lib/python2.7/site-packages')
import cv2

the ImportError:.. issue solved

3. Permanent solution

Create an iPython profile and set initial append:

In bash shell:

ipython profile create
... CHECK the path prompted , and edit the prompted config file like my case
vi /home/osboxes/.ipython/profile_default/ipython_kernel_config.py

In vi, append to the file:

c.InteractiveShellApp.exec_lines = [
 'import sys; sys.path.append("/home/osboxes/miniconda2/lib/python2.7/site-packages")'
]

DONE

Answer 6

Before installing ipython, I installed modules through easy_install; say sudo easy_install mechanize.

After installing ipython, I had to re-run easy_install for ipython to recognize the modules.

Answer 7

If you are running it from command line, sometimes python interpreter is not aware of the path where to look for modules.

Below is the directory structure of my project:

/project/apps/..
/project/tests/..

I was running below command:

>> cd project

>> python tests/my_test.py

After running above command i got below error

no module named lib

lib was imported in my_test.py

i printed sys.path and figured out that path of project i am working on is not available in sys.path list

i added below code at the start of my script my_test.py .

import sys
import os

module_path = os.path.abspath(os.getcwd())    

if module_path not in sys.path:       

    sys.path.append(module_path)

I am not sure if it is a good way of solving it but yeah it did work for me.

Answer 8

Had a similar problem, fixed it by calling python3 instead of python, my modules were in Python3.5.

Answer 9

I have found that the solution to this problem was extensively documented here:

https://jakevdp.github.io/blog/2017/12/05/installing-python-packages-from-jupyter/

Basically, you must install the packages within the Jupyter environment, issuing shell commands like:

!{sys.executable} -m pip install numpy

Please check the above link for an authoritative full answer.

Answer 10

This is how I fixed it:

import os
import sys
module_path = os.path.abspath(os.getcwd() + '\\..')
if module_path not in sys.path:
    sys.path.append(module_path)

Answer 11

I found yet another source of this discrepancy:

I have ipython installed both locally and in commonly in virtualenvs. My problem was that, inside a newly made virtualenv with ipython, the system ipython was picked up, which was a different version than the python and ipython in the virtualenv (a 2.7.x vs. a 3.5.x), and hilarity ensued.

I think the smart thing to do whenever installing something that will have a binary in yourvirtualenv/bin is to immediately run rehash or similar for whatever shell you are using so that the correct python/ipython gets picked up. (Gotta check if there are suitable pip post-install hooks...)

Answer 12

Solution without scripting:

1. Open Spyder -> Tools -> PYTHONPATH manager
2. Add Python paths by clicking "Add Path". E.g: 'C:\Users\User\AppData\Local\Programs\Python\Python37\Lib\site-packages'
3. Click "Synchronize..." to allow other programs (e.g. Jupyter Notebook) use the pythonpaths set in step 2.
4. Restart Jupyter if it is open

Answer 13

This is probably caused by different python versions installed on your system, i.e. python2 or python3.

Run command $ pip --version and $ pip3 --version to check which pip is from at Python 3x. E.g. you should see version information like below:

pip 19.0.3 from /usr/local/lib/python3.7/site-packages/pip (python 3.7)

Then run the example.py script with below command

$ python3 example.py

Answer 14

remove pathlib and reinstall it.

Delete the pathlib in sitepackages folder and reinstall the pathlib package by using pip command.

pip install pathlib