如何在conda环境中将python 2.7替换为3.6？

Question

I created a conda environment named AAA with python 2.7 long ago and I want to update the python to 3.6 without any change of other packages in AAA. I try conda install python=3.6 in AAA, but all packages were emptied. What should I do to solve it?

Answer 1

you'll have to reinstall packages for python 3.7. So it's better way to create new venv under 3.7. you can you pip freeze to get the list of installed packages and put it into requirements.txt file. then use it with pip3 install -r requirements.txt command. This will install them

more to that there's pip3 specially for python3.* which installs compatible packages.

BTW be aware that python2 code is not compatible with python3

Answer 2

As @StanislavLipovenko pointed out , Python 2.7 packages can't run under Python 3.6 (they're installed to a different site-packages directory and usually aren't co-compatible), so you need a fresh install.

One option is to export your env configuration as a YAML:

conda env export -n my_py27_env --no-builds > my_env.yaml

Edit the line with - python=2.7.* to - python=3.6 . Then create a new env from this:

conda env create -f my_env.yaml -n my_py36_env

You may have some hiccups getting all the packages listed in the YAML to install, especially if your original env is quite old. For example, a package that had a Python 2.7 version may never have released that same version for Python 3.6. You can always soften the requirements by deleting the version numbers in the YAML for packages that present such barriers. This is simply the unavoidable cost of transitioning.