I installed a python package using /usr/local/bin/python3.6 -m pip install flask_Humanify and it gave me the output below, indicating that everything worked. Now, when I run my code /usr/local/bin/python3.6 test.py I get Traceback (most recent call last): File "once.py", line 29, in <module> from flask_Humanify import Humanify ModuleNotFoundError: No module named 'flask_Humanify' but I am sure it uses the same python? /usr/local/bin/python3.6 --version Python 3.6.3 /usr/local/bin/python3.6 -m pip --version pip 21.3.1 from /usr/local/lib/python3.6/site-packages/pip (python 3.6) I can also see it in pip list -v ... flask-Humanify 0.2.3 /usr/local/lib/python3.6/site-packages pip ... Output after /usr/local/bin/python3.6 -m pip install flask_Humanify Requirement already satisfied: flask_Humanify in /usr/local/lib/python3.6/site-packages (0.2.3) Requirement already satisfied: cryptography in /usr/local/lib/python3.6/site-packages (from flask_Humanify) (40.0.2) Requirement already satisfied: opencv-python-headless in /usr/local/lib/python3.6/site-packages (from flask_Humanify) (4.5.5.64) Requirement already satisfied: numpy in /usr/local/lib/python3.6/site-packages (from flask_Humanify) (1.17.4) Requirement already satisfied: pydub in /usr/local/lib/python3.6/site-packages (from flask_Humanify) (0.25.1) Requirement already satisfied: Flask in /usr/local/lib/python3.6/site-packages (from flask_Humanify) (1.1.1) Requirement already satisfied: netaddr in /usr/local/lib/python3.6/site-packages (from flask_Humanify) (0.10.1) Requirement already satisfied: scipy in /usr/local/lib/python3.6/site-packages (from flask_Humanify) (1.3.3) Requirement already satisfied: cffi>=1.12 in /usr/local/lib/python3.6/site-packages (from cryptography->flask_Humanify) (1.15.1) Requirement already satisfied: Jinja2>=2.10.1 in /usr/local/lib/python3.6/site-packages (from Flask->flask_Humanify) (2.10.3) Requirement already satisfied: Werkzeug>=0.15 in /usr/local/lib/python3.6/site-packages (from Flask->flask_Humanify) (0.16.0) Requirement already satisfied: click>=5.1 in /usr/local/lib/python3.6/site-packages (from Flask->flask_Humanify) (7.0) Requirement already satisfied: itsdangerous>=0.24 in /usr/local/lib/python3.6/site-packages (from Flask->flask_Humanify) (1.1.0) Requirement already satisfied: importlib-resources in /usr/local/lib/python3.6/site-packages (from netaddr->flask_Humanify) (5.4.0) Requirement already satisfied: pycparser in /usr/local/lib/python3.6/site-packages (from cffi>=1.12->cryptography->flask_Humanify) (2.21) Requirement already satisfied: MarkupSafe>=0.23 in /usr/local/lib/python3.6/site-packages (from Jinja2>=2.10.1->Flask->flask_Humanify) (1.1.1) Requirement already satisfied: zipp>=3.1.0 in /usr/local/lib/python3.6/site-packages (from importlib-resources->netaddr->flask_Humanify) (3.6.0) WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv Continue reading...