numpy not importing in python3.7 virtualenv

Reproducing code example:

import numpy

Error message:

Traceback (most recent call last):
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/__init__.py", line 17, in <module>
    from . import multiarray
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/multiarray.py", line 14, in <module>
    from . import overrides
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/overrides.py", line 7, in <module>
    from numpy.core._multiarray_umath import (
ImportError: libf77blas.so.3: cannot open shared object file: No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "main_commandline.py", line 7, in <module>
    import numpy as np
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/__init__.py", line 142, in <module>
    from . import core
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/__init__.py", line 47, in <module>
    raise ImportError(msg)
ImportError: 

IMPORTANT: PLEASE READ THIS FOR ADVICE ON HOW TO SOLVE THIS ISSUE!

Importing the numpy c-extensions failed.
- Try uninstalling and reinstalling numpy.
- If you have already done that, then:
  1. Check that you expected to use Python3.7 from "/home/pi/.virtualenvs/print3.7/bin/python",
     and that you have no directories in your PATH or PYTHONPATH that can
     interfere with the Python and numpy version "1.17.2" you're trying to use.
  2. If (1) looks fine, you can open a new issue at
     https://github.com/numpy/numpy/issues.  Please include details on:
     - how you installed Python
     - how you installed numpy
     - your operating system
     - whether or not you have multiple versions of Python installed
     - if you built from source, your compiler versions and ideally a build log

- If you're working with a numpy git repository, try `git clean -xdf`
  (removes all files not under version control) and rebuild numpy.

Note: this error has many possible causes, so please don't comment on
an existing issue about this - open a new one instead.

Original error was: libf77blas.so.3: cannot open shared object file: No such file or directory

Numpy/Python version information:

>>> import sys, numpy; print(numpy.__version__, sys.version)
Traceback (most recent call last):
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/__init__.py", line 17, in <module>
    from . import multiarray
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/multiarray.py", line 14, in <module>
    from . import overrides
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/overrides.py", line 7, in <module>
    from numpy.core._multiarray_umath import (
ImportError: libf77blas.so.3: cannot open shared object file: No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/__init__.py", line 142, in <module>
    from . import core
  File "/home/pi/.virtualenvs/print3.7/lib/python3.7/site-packages/numpy/core/__init__.py", line 47, in <module>
    raise ImportError(msg)
ImportError: 

IMPORTANT: PLEASE READ THIS FOR ADVICE ON HOW TO SOLVE THIS ISSUE!

Importing the numpy c-extensions failed.
- Try uninstalling and reinstalling numpy.
- If you have already done that, then:
  1. Check that you expected to use Python3.7 from "/home/pi/.virtualenvs/print3.7/bin/python",
     and that you have no directories in your PATH or PYTHONPATH that can
     interfere with the Python and numpy version "1.17.2" you're trying to use.
  2. If (1) looks fine, you can open a new issue at
     https://github.com/numpy/numpy/issues.  Please include details on:
     - how you installed Python
     - how you installed numpy
     - your operating system
     - whether or not you have multiple versions of Python installed
     - if you built from source, your compiler versions and ideally a build log

- If you're working with a numpy git repository, try `git clean -xdf`
  (removes all files not under version control) and rebuild numpy.

Note: this error has many possible causes, so please don't comment on
an existing issue about this - open a new one instead.

Original error was: libf77blas.so.3: cannot open shared object file: No such file or directory

Info that the error message requested:

 - how you installed Python: Python3.7 comes pre-installed with Raspbian Buster. Made a virtualenv using 3.7
 - how you installed numpy: In my venv, `pip3 install numpy`
 - your operating system: Raspbian Buster, apt-get updated and upgraded.
 - whether or not you have multiple versions of Python installed: 2.7 and 3.7 by default.  Added 3.6 myself (sudo apt-get install python3.6-dev) but am not using it for this.

[EdwardChamberlain]

I also had this issue. For me running sudo apt-get install libatlas-base-dev fixed it. It seems this is an issue with piwheels.

[Danie12345]

I believe it was just one of those situations where the selected environment was not being used. And running that piece of code confirms it. I’ve managed to get around it by running the file with a button, which finds the file and runs it using the selected environment for me.

Sorry for the trouble, and thank you!