Python / pip错误的解释器：没有这样的文件或目录

Question

I seem to have lost all the python packages that I had on my Mac.

I entered the command below to upgrade from python3.6 to python3.7:

brew upgrade python

and now when I enter ipython3 in the terminal it says:

-bash: /usr/local/bin/ipython3: /usr/local/opt/python/bin/python3.6: bad interpreter: No such file or directory

However I was able to use ipython3 moments before I performed the brew upgrade. Furthermore, I think I have lost all my python packages because when I do an import module in Python3, it says:

ModuleNotFoundError: No module named *examplepythonpackage*

Are the python packages that I installed before all lost for good and do I have to re-install them individually now?

I also cannot run (in the bash terminal) $ ipython3

-bash: /usr/local/bin/ipython3: /usr/local/opt/python/bin/python3.6: bad interpreter: No such file or directory

For reference:

$ which python
    /usr/bin/python
$ which python3
    /usr/local/bin/python3
$ pip --version
    pip 18.1 from /Library/Python/2.7/site-packages/pip-18.1-py2.7.egg/pip (python 2.7)
$ pip3 --version
    pip 18.1 from /usr/local/lib/python3.7/site-packages/pip (python 3.7)

Answer 1

The link between ipython and which Python interpreter and libraries it uses underneath is established at installation time (as opposed to dynamically every time you run it), so I think your problem will be resolved if you remove and then re-install ipython , ie:

brew rm ipython
brew install ipython

If you want to understand this, look at your ipython script like this:

more $(which ipython)

Answer 2

Your packages are not gone but are invisible to your new python. You might try to trick python 3.7 into looking for packages inside the python3.6 directory but then many packages would not work, specifically extension packages since 3.6 and 3.7 are not ABI compatible.

Basically, an upgrade like this requires you to reinstall all packages.