Installing lxml on Python 3 on a Mac

Question

I have a new Mac and I installed python 3 using brew install python .

[~]$ which python3                                                rbenv:system 
/usr/local/bin/python3

[~]$ python3 --version                                            rbenv:system 
Python 3.8.6

I ran the following command: pip3 install -r requirements.txt which has lxml==4.5.2 in it.

It installed fine with no errors. If I run it again I get this:

Requirement already satisfied: lxml==4.5.2 in /usr/local/lib/python3.9/site-packages (from -r requirements.txt (line 1)) (4.5.2)

However whenever I try to import lxml, I get an error:

[~]$ python3                                                      rbenv:system 
Python 3.8.6 (default, Oct  8 2020, 14:06:32) 
[Clang 12.0.0 (clang-1200.0.32.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import lxml
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'lxml'
>>> 

Any ideas how to resolve this, I am using ohmyZSH so do I need to add anything to my .zshrc?

Some info on pip3:

*[master][~/src/Arelle]$ which pip3                               rbenv:system 
/usr/local/bin/pip3
*[master][~/src/Arelle]$ pip3 --version                           rbenv:system 
pip 20.2.3 from /usr/local/lib/python3.9/site-packages/pip (python 3.9)

Answer 1

The problem is that python3 and pip3 can be binaries that use different versions of Python. Furthermore, there are virtual environments, which give you a local site-packages (folder for installed packages).

The best way to use pip COMMAND is with python3 -m pip COMMAND . That way you always know what Python installation your pip is doing work for.

In your case, run

python3 -m pip install lxml

in order to get lxml where you want it.