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Anaconda environment with a python specific [duplicate]

I have miniconda3 installed and since I would like to have an environment with python version 3.3.0, I create it via
conda create -n "myenv" python=3.3.0
However when I activate the environment via
conda activate myenv
python has version 2.7.15 and path
/usr/bin/python
and ipython has python version 3.6.8 and path
/home/myname/.local/bin/ipython
I can access the correct python with python3 which is at
/home/myname/miniconda3/envs/myenv/bin/python3
however, ipython3 has python version 3.6.8 again.
conda install python=3.3.0
left the situation unchanged.
A solution would be to open IPython via
python3 -m IPython
however, while this works fine for python here I get the error message
/home/myname/miniconda3/envs/myenv/bin/python3: No module named IPython
Is it possible to access with the commands python and ipython both python version 3.3.0 in that specific environment, i.e. not by setting an alias in the .bashrc?
EDIT:
Turns out that this problem does not occur if you select version 3.3 instead of 3.3.0 together with #ilmarinen's answer
conda create -n "myenv" python=3.3 ipython
everything works fine and python as well as ipython result to version python 3.3.5.

You need to install ipython as well into your given environment
conda create -n "myenv" python=3.3.0 ipython
The conda environments are prepended to your PATH variable, so when you are trying to run the executable "ipython", Linux will not find "ipython" in your activated environment (since it doesn't exist there), but it will continue searching for it, and eventually find it wherever you have it installed.

To create an environment named py33 with python 3.3.0, using the channel conda-forge and a list of packages:
conda create -y --name py33 python==3.3.0
conda install -f -y -q --name py33 -c conda-forge --file requirements.txt
conda activate py33
...
conda deactivate
Alternatively you can use
conda env create -f environment.yml
for using an environment.yml file instead of requirements.txt:
name: py33
channels:
- conda-forge
dependencies:
- python==3.3.0
- ipython
Use this command to remove the environment:
conda env remove -n py33

I had similar issue. And I could't find many useful discussions.
The problem for me was I have alias pointing python to miniconda python hardcoded in my shell config file when I execute conda init zsh. Somehow the init process copies the alias and always reload that, thus overwrites the "correct" version.
After conda create -n py27 python=2.7 (my system default is 3.6), the version was correctly installed at miniconda3/envs/py27/bin/python. But the activated evironment python was not pointing to it, as indicated by which python,even if I deleted updated my shell config.
In the end it was solved by 'reverse' conda init (remove the generated conda function in .zshrc), remove alias, and re-init.
I guess other shell is using the same mechanism.

conda install downgrade python version

I'm trying to downgrade python version of anaconda via conda install python=3.3, but have following error:
~/anaconda3/bin$ ./conda install python=3.3
Fetching package metadata .........
Solving package specifications: .
UnsatisfiableError: The following specifications were found to be in conflict:
- gevent -> python 2.6*
- python 3.3*
Use "conda info <package>" to see the dependencies for each package.
How to resolve conflicts with the packages?

If you want to set specific version, use it like this:
WARNING: This command will overwrite the default python version system-wise
conda install python=3.6
To create environment with a specific version, you can do:
conda create -n $PYTHON36_ENV_NAME python=3.6 anaconda # set custom env name
The anaconda at the end allows the env to use all anaconda packages
For more information refere to Anaconda documentation

There are two ways to downgrade python in anaconda.
1. Downgrade python in the active environment
(This can lead to conflicts with installed packages for higher python versions)
conda activate nameOfYourEnvironment
conda install python=3.3
2. Create a new environment
(This is a more safer way, but you need to install all necessary packages again)
conda activate base
conda create --name env_name python=3.3
Hint: Use conda list before creating a new environment to get the names of all installed packages in the actual environment.
If you want to check your installed environments do:
conda env list
If you got problems in installing, make sure to run the shell as administrator (always recommended).

You can make environments with other versions of Python using this command:
conda create --name py33 python=3.3
source activate py33

Very firstly check the current version using command python --version. Then on anaconda prompt type the command conda search python which will list all the python versions available till date. Then from that list select your version and type conda install python=3.5.2 or any of your choice

How do I install a package for different Python versions in Anaconda?

I have Python 2.7 as root. I need to install the package "statistics" in Python 3.6, and it is not in the environments of anaconda navigator. How can install "statistics" with conda or pip for a secondary Python environment?

Create a new Python 3 environment by running:
conda create --name python3 python=3
If you want all the standard anaconda packages installed by default, do:
conda create --name python3 python=3 anaconda
Whenever you need to use python3 run:
activate python3
Then use the command line as normal. So, if you want to install something into your python3 environment, make sure you activate python3 first.
Note that python 3 has it's own statistics module that you may find useful, and this module has been ported to python 2 if you would prefer.

How do I upgrade to Python 3.6 with conda?

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?

Anaconda had not updated Python internally to 3.6, but later versions of Anaconda has a Python 3.6 version here.
a) Method 1
If you wanted to update, you will type conda update python
To update Anaconda, type conda update conda
If you want to upgrade between major python versions, like 3.5 to 3.6, you'll have to do
conda install python=$pythonversion$
b) Method 2 - Create a new environment (the better method)
conda create --name py36 python=3.6
c) To get the absolute latest Python (3.6.5 at time of writing)
conda create --name py365 python=3.6.5 --channel conda-forge
You can see all this from here.
Also, refer to this for force upgrading.

Creating a new environment will install Python 3.6:
conda create --name 3point6 python=3.6
Output:
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

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 says 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

I'm using macOS v10.14 (Mojave).
These four steps worked for me.
conda update conda
conda install python=3.6
conda install anaconda-client
conda update anaconda

If you want to upgrade the Python version inside your existing environment, activate it first with conda activate <env_name> and then do:
conda install -c anaconda python=<version>
You might also need to update the dependencies with
conda update --all

This is how I manage to get (as currently there isn't any direct support. In the future, it will be for sure) Python 3.9 in earlier versions of 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
Python 3.9 is available with later versions of conda. Use the below command:
conda create --name <myenv> python=3.9
And it will create your Python 3.9 virtual environment simply.

The only solution that works was creating a new Conda environment with the name you want (you will, unfortunately, delete the old one to keep the name). Then create a new environment with a new Python version and rerun 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 world ;)
Note the below doesn't work:
If you want to update the Conda version of your previous environment you can also do the following (more complicated than it should be because you cannot rename environments in Conda):
create a temporary new location for your current environment:
conda create --name temporary_env_name --clone original_env_name
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`
then create the new empty environment with the Python version you want and clone the original environment:
conda create --name original_env_name python=3.8 --clone temporary_env_name

Open an Anaconda PowerShell prompt as an administrator user.
Type in conda update python.
Wait about 10 minutes. In this process, you may need to type in y at some time.
After completing, check your Python version in Conda by typing python --version
If it is the newest version, then you can restart your computer.

The 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...

Decrementing Python

I've got a package that depends on an earlier version of Python -- I'm running 3.5.1, but the package only supports up through Python 3.4. I'd like to clone my current environment, decrement my Python version to 3.4, and then update all other packages to the latest version compatible with Python 3.4. How do I do that?
When I clone my root environment and attempt:
conda install python=3.4
I receive the message:
Error: 'conda' can only be installed into the root directory.
I'm working on Windows currently. Any ideas would be much appreciated.

Create a new environment:
conda create -n py34 python=3.4
activate it:
source activate py34
(no source on Windows)
Install all your packages:
(py34) conda install package1 package2
This keeps your original Python 3.5 install and you can activate Python 3.4 whenever you need it. Deactivate with deactivate.
You can export names and versions of all packages you have currently installed with:
conda list --export > list_of_my_packages
Use this file to create your new py34 environment:
conda create --file list_of_my_packages -n py34 python=3.4
You might get a warning about packages missing form the current channels.
Either add more channels or edit this list, opening the file in an editor.
Finally, you can update all packages to the latest version with:
conda update all