python - Module installed with PIP in virtualenv not found

Question

Getting a very strange error. I am making a virtual environment and initializing it with a pip requirements.txt file, but when I go to run code in the activated environment, the virtual environment interpreter claims to be missing some (and only some) of the modules:

(venv) $ pip list
certifi (2017.7.27.1)
chardet (3.0.4)
decorator (4.1.2)
idna (2.5)
ipython (6.1.0)
ipython-genutils (0.2.0)
jedi (0.10.2)
numpy (1.13.1)
olefile (0.44)
pexpect (4.2.1)
pickleshare (0.7.4)
Pillow (4.2.1)
pip (9.0.1)
prompt-toolkit (1.0.15)
protobuf (3.3.0)
ptyprocess (0.5.2)
Pygments (2.2.0)
PyYAML (3.12)
pyzmq (16.0.2)
requests (2.18.3)
scipy (0.19.1)
setuptools (38.5.1)
simplegeneric (0.8.1)
six (1.10.0)
torch (0.2.0.post3)
torchvision (0.2.0)
tornado (4.5.1)
tqdm (4.15.0)
traitlets (4.3.2)
urllib3 (1.22)
visdom (0.1.5)
wcwidth (0.1.7)
wheel (0.30.0)

So I double check:

(venv) $ pip install tqdm?
Requirement already satisfied: tqdm in ./venv/lib/python3.6/site-packages
(venv) $ python ?
Python 3.6.3 |Anaconda custom (64-bit)| (default, Oct 13 2017, 12:02:49) 
[GCC 7.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from tqdm import tqdm
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'tqdm'

people have suggested forcing a reinstall, using a different interpreter source, and just reinstalling. None of these have worked. this is very mysterious. Have any of you seen anything like this? Saw a similar unresolved problem here

UPDATE: Fixed. H/T to @Riverman for helping my find the issue: the problem was that an old unused alias was left over from a while ago, and while pip still had it own point back to python3.6, the python command itself was aliased to some old Anaconda3 version I had lying around somewhere. Alias, I forgot, do not go away by just re-sourcing your .bashrc file, so I ran unalias with the offending python command and it worked!

Would still love to hear from people though if they could explain why this can occur, though. I though venv completely insulated you from the outside environment...is it because aliasing is a system level effect so it seeps into the venv??

Answer 1

While being inside the virtualenv, please issue the following commands:

• pip freeze
• pip -V
• python -V
• which python
• which pip

Share your results here to analyze it. I've also experienced pretty similar issues with the requests package before, but that happened on windows to me.