When importing Numpy from Flask in Virtualenv Numpy gives multiarray import error

Question

I'am trying to import numpy at flask `__init__.py` but it gives this error : ``` Importing the multiarray numpy extension module failed. Most likely you are trying to import a failed build of numpy. If you're working with a numpy git repo, try `git clean -xdf` (removes all files not under version control). Otherwise reinstall numpy. ``` When I remove the import from flasks `__init__.py` everything works. When I do `from numpy.core import multiarray` in virtualenv everything works but importing it from wsgi is not working. here is the apache/site-available config file: ``` ServerName 192.168.0.1 ServerAdmin hello@world.com WSGIScriptAlias / /home/bar/FlaskApp/FlaskApp/FlaskApp.wsgi Require all granted Alias /static /home/bar/FlaskApp/FlaskApp/static Require all granted ErrorLog ${APACHE_LOG_DIR}/error.log LogLevel warn CustomLog ${APACHE_LOG_DIR}/access.…

Accepted Answer

Imports under mod_wsgi can be tricky, particularly with Python C extension libraries.

The issue here turned out to be setting the `WSGIDaemonProcess` `python-path=` option to a venv with the compiled module. From those docs:

If using a Python virtual environment, rather than use this option to refer to the site-packages directory of the Python virtual environment, you should use the python-home option to specify the root of the Python virtual environment instead.

In all cases, if the directory contains Python packages which have C extension components, those packages must have been installed using the same base Python version as was used to compile the mod_wsgi module. You should not mix packages from different Python versions or installations.

So, the `python-home=` option must be used for the venv dir given, and either Python 2.7 should be used for the venv, or the Python 3 build of mod_wsgi must be installed (`libapache2-mod-wsgi-py3` on Ubuntu).

For some applications, the `WSGIApplicationGroup` needs to be configured as follows too:

```
WSGIApplicationGroup %{GLOBAL}
```

In the case that any of the C extensions use the simplified threading api.

From similar questions, α, β, this seems to be a common issue.

When importing Numpy from Flask in Virtualenv Numpy gives multiarray import error

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