I’ve installed Anaconda and created two extra environments: py3k (which holds Python 3.3) and py34 (which holds Python 3.4). Besides those, I have a default environment named ‘root’ which the Anaconda installer created by default and which holds Python 2.7. This last one is the default, whenever I launch ‘ipython’ from the terminal it gives me version 2.7. In order to work with Python 3.4, I need to issue the commands (in the shell)

source activate py34
ipython

which change the default environment to Python 3.4. This works fine, but it’s annoying since most of the time I work on Python 3.4, instead of Python 2.7 (which I hold for teaching purposes, it’s a rather long story). Anyway, I’ll like to know how to change the default environment to Python 3.4, bearing in mind that I don’t want to reinstall everything from scratch.

If you just want to change to another environment, use

source activate environment-name

(you can create environment-name with `conda create)

Typically it’s best to just create new environments. However, if you really want to change the Python version in the default environment, you can do so as follows:

First, make sure you have the latest version of conda by running

conda update conda

Then run

conda install python=3.5

This will attempt to update all your packages in your root environment to Python 3 versions. If it is not possible (e.g., because some package is not built for Python 3.5), it will give you an error message indicating which package(s) caused the issue.

If you installed packages with pip, you’ll have to reinstall them.

Overview
Some people have multiple Anaconda environments with different versions of python for compatibility reasons. In this case, you should have a script that sets your default environment. With this method, you can preserve the versions of python you use in your environments.

The following assumes environment_name is the name of your environment

Mac / Linux:
Edit your bash profile so that the last line is source activate environment_name. In Mac OSX this is ~/.bash_profile, in other environments this may be ~/.bashrc

Example:
Here’s how i did it on Mac OSX

1. Open Terminal and type:

   nano ~/.bash_profile

2. Go to end of file and type the following, where “p3.5” is my environment:

   source activate p3.5

3. Exit File. Start a new terminal window.

4. Type the following to see what environment is active

   conda info -e

The result shows that I’m using my p3.5 environment by default.

For Windows:
Create a command file (.cmd) with activate environment_name and follow these instructions to have it execute whenever you open a command prompt

1. Create a batch file command, e.g. “my_conda.cmd”, put it in the Application Data folder.
2. Configure it to be started automatically whenever you open cmd. This setting is in Registry:
   key: HKCU\SOFTWARE\Microsoft\Command Processor
   value: AutoRun
   type: REG_EXPAND_SZ
   data: “%AppData%\my_conda.cmd”

from this answer: https://superuser.com/a/302553/143794

Under Linux there is an easier way to set the default environment by modifying ~/.bashrc or ~/.bash_profile At the end you’ll find something like

# added by Anaconda 2.1.0 installer
export PATH="~/anaconda/bin:$PATH"

Replace it with

# set python3 as default
export PATH="~/anaconda/envs/python3/bin:$PATH"

and thats all there is to it.

For windows Anaconda comes with Anaconda Prompt which is a shortcut to cmd and can be used run conda commands without adding anaconda in PATH variable. Find the location of it, copy and rename the copy (say myenv_prompt). Right click myenv_prompt and select properties in the context menu.

The Target form of Properties window should already be filled with text, something like %windir%\system32\cmd.exe "/K" C:\Users\xxx\AppData\Local\Continuum\Miniconda3\Scripts\activate.bat C:\Users\xxx\AppData\Local\Continuum\Miniconda3\ There are three parts of this command 1)start …\cmd.exe 2)run …\acitvate.bat with environment 3)…\Miniconda3\

Change 3rd part to path of the environment (say myenv) you want as default i.e. fill the Target form something like %windir%\system32\cmd.exe "/K" C:\Users\xxx\AppData\Local\Continuum\Miniconda3\Scripts\activate.bat C:\Users\xxx\AppData\Local\Continuum\Miniconda3\envs\myenv

Now myenv_prompt will act as shortcut to start cmd with myenv as the default environment for python. This shortcut you can keep in start menu or pinned in taskbar.

One advantage of this method is that you can create a few shortcuts each having different environment as default environment. Also you can set the default folder by filling Start in form of the Properties window

Hope this helps

PS:It is not required to find Anaconda Prompt and can be done by changing target of any shortcut. But you will require to know path of cmd.exe and activate.bat

Change permanent

conda install python={version}

Change Temporarily

View your environments

run conda info --envs on your terminal window or an Anconda Prompt

If It doesn’t show environment that you want to install

run conda create -n py36 python=3.6 anaconda for python 3.6 change version as your prefer

Activating an environment (use Anaconda prompt)

run activate envnme envnme you can find by this commandconda info --envs as a example when you run conda info --envs it show

base * C:\Users\DulangaHeshan\Anaconda3 py36 C:\Users\DulangaHeshan\Anaconda3\envs\py36

then run activate py36

to check run python --version

In Windows, it is good practice to deactivate one environment before activating another. https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html?highlight=deactivate%20environment

The correct answer (as of Dec 2018) is… you can’t. Upgrading conda install python=3.6 may work, but it might not if you have packages that are necessary, but cannot be uninstalled.

Anaconda uses a default environment named base and you cannot create a new (e.g. python 3.6) environment with the same name. This is intentional. If you want your base Anaconda to be python 3.6, the right way to do this is to install Anaconda for python 3.6. As a package manager, the goal of Anaconda is to make different environments encapsulated, hence why you must source activate into them and why you can’t just quietly switch the base package at will as this could lead to many issues on production systems.

I wasn’t satisfied with any of the answers presented here, since activating an environment takes a few seconds on my platform (for whatever reason)

I modified my path variable so that the environment I want as default has priority over the actual default.

In my case I used the following commands to accomplish that for the environment “py35”:

setx PATH "%userprofile%\Anaconda3\envs\py35\;%PATH%"
setx PATH "%userprofile%\Anaconda3\envs\py35\Scripts;%PATH%"

to find out where your environment is stored, activate it and enter where python. I’m not sure yet if this approach has any downsides. Since it also changes the default path of the conda executable. If that should be the case, please comment.

I got this when installing a library using anaconda. My version went from Python 3.* to 2.7 and a lot of my stuff stopped working. The best solution I found was to first see the most recent version available:

conda search python

Then update to the version you want:

conda install python=3.*.*

Source: http://chris35wills.github.io/conda_python_version/

Other helpful commands:

conda info
python --version

Create a shortcut of anaconda prompt onto desktop or taskbar, and then in the properties of that shortcut make sure u modify the last path in “Target:” to the path of ur environment:

C:\Users\BenBouali\Anaconda3\ WILL CHANGE INTO C:\Users\BenBouali\Anaconda3\envs\tensorflow-gpu

preview

and this way u can use that shortcut to open a certain environment when clicking it, you can add it to ur path too and now you’ll be able to run it from windows run box by just typing in the name of the shortcut.

On Windows, create a batch file with the following line in it:

start cmd /k "C:\Anaconda3\Scripts\activate.bat C:\Anaconda3 & activate env"

The first path contained in quotes is the path to the activate.bat file in the Anaconda installation. The path on your system might be different. The name following the activate command of course should be your desired environment name.

Then run the batch file when you need to open an Anaconda prompt.

Load your “base” environment — as OP’s py34 — when you load your terminal/shell.

If you use Bash, put the line:

conda activate py34

in your .bash_profile (or .bashrc):

$ echo 'conda activate py34' >> ~/.bash_profile

Every time you run a new terminal, conda environment py34 will be loaded.