在开发时，为什么`pip install .`要比`python setup.py install`慢得多？

Question

While I'm developing a python package, a common loop for me is to edit a few files, then reinstall the package in my virtual environment and re-run tests:

python setup.py install && pytest tests

The python setup.py install part runs in 0.696 seconds.

I feel like I should be using pip for this, which also works but is MUCH slower than the previous command:

pip install . && pytest tests

Here pip install . runs in 42.006 seconds.

Is there any way to speed up a local development install of pip install . so it's on the order of python setup.py install ?

Answer 1

It is slow because it makes a full copy of the entire directory, including possibly big hidden dirs like .git, .hg, .idea, .vagrant etc.

See this open issue: https://github.com/pypa/pip/issues/2195