virtual environment - can import package without having it installed in my venv

Question

I have created a virtual environment in python in ubuntu in Raspberry Pi with:

python -m venv ./venv/myname

That gives me folderstructure:

   myFolder
        +-- venv
        +-- myApplication.py

Im activating my virtualenvironment running:

source venv/myname/bin/activate

What I dont understand is when I am running

python myApplication.py

I can run the application using python packages installed globally but not in my virtual environment. For example I can import numpy without having it installed in my virtual environment but globaly. I thought I needed to install everything within my virtual environment no matter if I have it globally or not. Do I misunderstand something here?

Im using python 3.7 This is my output from print(sys.path)

>>> import sys
>>> print(sys.path)
['', '/usr/lib/python37.zip', '/usr/lib/python3.7', '/usr/lib/python3.7/lib-dynload', '/home/pi/.local/lib/python3.7/site-packages', '/usr/local/lib/python3.7/dist-packages', '/usr/local/lib/python3.7/dist-packages/Adafruit_PCA9685-1.0.1-py3.7.egg', '/usr/lib/python3/dist-packages']
>>> 

UPDATE The virtual environment seems to be running after all with testing it with os.environ['VIRTUAL_ENV'] . Weird enough I can run packages I have not installed in my virtual environment. Here is output from my terminal:

(myenv) pi@raspberrypi:~/Desktop/myproject/myenv$ python
Python 3.7.3 (default, Jan 22 2021, 20:04:44)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ['VIRTUAL_ENV']
'/home/pi/Desktop/myproject/myenv'
>>> exit()
(myenv) pi@raspberrypi:~/Desktop/myproject/myenv$ deactivate
pi@raspberrypi:~/Desktop/myproject/myenv$ pythonPython 3.7.3 (default, Jan 22 2021, 20:04:44)
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ['VIRTUAL_ENV']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.7/os.py", line 678, in __getitem__
    raise KeyError(key) from None
KeyError: 'VIRTUAL_ENV'
>>>

Answer 1

It is very clear to me your virtual environment (venv) has not been activated (see this SO post for ways to verify).

You can run your programs without activating by running ./venv/myname/bin/python myApplication.py . However, you probably don't want to be using this everytime as it's verbose.

There can be a ton of system-specific reasons why your venv isn't being activated after running source . My recommendation is to first reinstall virtualenv, delete your venv, and recreate.