[python] How do I upgrade to Python 3.6 with conda?

I'm new to Conda package management and I want to get the latest version of Python to use f-strings in my code. Currently my version is (python -V):

Python 3.5.2 :: Anaconda 4.2.0 (x86_64)

How would I upgrade to Python 3.6?

I found this page with detailed instructions to upgrade Anaconda to a major newer version of Python (from Anaconda 4.0+). First,

conda update conda
conda remove argcomplete conda-manager

I also had to conda remove some packages not on the official list:

• backports_abc
• beautiful-soup
• blaze-core

Depending on packages installed on your system, you may get additional UnsatisfiableError errors - simply add those packages to the remove list. Next, install the version of Python,

conda install python==3.6

which takes a while, after which a message indicated to conda install anaconda-client, so I did

conda install anaconda-client

which said it's already there. Finally, following the directions,

conda update anaconda

I did this in the Windows 10 command prompt, but things should be similar in Mac OS X.

In the past, I have found it quite difficult to try to upgrade in-place.

Note: my use-case for Anaconda is as an all-in-one Python environment. I don't bother with separate virtual environments. If you're using conda to create environments, this may be destructive because conda creates environments with hard-links inside your Anaconda/envs directory.

So if you use environments, you may first want to export your environments. After activating your environment, do something like:

conda env export > environment.yml

After backing up your environments (if necessary), you may remove your old Anaconda (it's very simple to uninstall Anaconda):

$ rm -rf ~/anaconda3/

and replace it by downloading the new Anaconda, e.g. Linux, 64 bit:

$ cd ~/Downloads
$ wget https://repo.continuum.io/archive/Anaconda3-4.3.0-Linux-x86_64.sh 

(see here for a more recent one),

and then executing it:

$ bash Anaconda3-4.3.0-Linux-x86_64.sh 

This is how I mange to get (as currently there is no direct support- in future it will be for sure) python 3.9 in anaconda and windows 10
Note: I needed extra packages so install them, install only what you need

conda create --name e39 python=3.9 --channel conda-forge

Creating a new environment will install python 3.6:

$ conda create --name 3point6 python=3.6
Fetching package metadata .......
Solving package specifications: ..........

Package plan for installation in environment /Users/dstansby/miniconda3/envs/3point6:

The following NEW packages will be INSTALLED:

    openssl:    1.0.2j-0     
    pip:        9.0.1-py36_1 
    python:     3.6.0-0      
    readline:   6.2-2        
    setuptools: 27.2.0-py36_0
    sqlite:     3.13.0-0     
    tk:         8.5.18-0     
    wheel:      0.29.0-py36_0
    xz:         5.2.2-1      
    zlib:       1.2.8-3 

Best method I found:

source activate old_env
conda env export > old_env.yml

Then process it with something like this:

with open('old_env.yml', 'r') as fin, open('new_env.yml', 'w') as fout:
    for line in fin:
        if 'py35' in line:  # replace by the version you want to supersede
            line = line[:line.rfind('=')] + '\n'
        fout.write(line)

then edit manually the first (name: ...) and last line (prefix: ...) to reflect your new environment name and run:

conda env create -f new_env.yml

you might need to remove or change manually the version pin of a few packages for which which the pinned version from old_env is found incompatible or missing for the new python version.

I wish there was a built-in, easier way...

I'm using a Mac OS Mojave

These 4 steps worked for me.

1. conda update conda
2. conda install python=3.6
3. conda install anaconda-client
4. conda update anaconda

Only solution that works was create a new conda env with the name you want (you will, unfortunately, delete the old one to keep the name). Then create a new env with a new python version and re-run your install.sh script with the conda/pip installs (or the yaml file or whatever you use to keep your requirements):

conda remove --name original_name --all
conda create --name original_name python=3.8
sh install.sh  # or whatever you usually do to install dependencies

doing conda install python=3.8 doesn't work for me. Also, why do you want 3.6? Move forward with the word ;)

Note bellow doesn't work:

If you want to update the conda version of your previous env what you can also do is the following (more complicated than it should be because you cannot rename envs in conda):

1. create a temporary new location for your current env:

conda create --name temporary_env_name --clone original_env_name

2. delete the original env (so that the new env can have that name):

conda deactivate
conda remove --name original_env_name --all # or its alias: `conda env remove --name original_env_name`

3. then create the new empty env with the python version you want and clone the original env:

conda create --name original_env_name python=3.8 --clone temporary_env_name