Unable to set default python version to python3 in ubuntu
PythonPython 3.xUbuntuInstallationUbuntu 16.04Python Problem Overview
I was trying to set default python version to python3 in Ubuntu 16.04. By default it is python2 (2.7). I followed below steps :
update-alternatives --remove python /usr/bin/python2
update-alternatives --install /usr/bin/python python /usr/bin/python3
but I'm getting the following error for the second statement,
rejeesh@rejeesh-Vostro-1015:~$ update-alternatives --install /usr/bin/python python /usr/bin/python3
update-alternatives: --install needs <link> <name> <path> <priority>
Use 'update-alternatives --help' for program usage information.
I'm new to Ubuntu and Idon't know what I'm doing wrong.
Python Solutions
Solution 1 - Python
The second line mentioned can be changed to
[sudo] update-alternatives --install /usr/bin/python python /usr/bin/python3 10
This gives a priority of 10 for the path of python3.
The disadvantage of alternatively editing .bashrc is that using the commands with sudo will not work.
Solution 2 - Python
EDIT:
I wrote this when I was young and naive, update-alternatives is the better way to do this. See @Pardhu's answer.
Outdated answer:
> Open your .bashrc file nano ~/.bashrc. Type alias python=python3
> on to a new line at the top of the file then save the file with ctrl+o
> and close the file with ctrl+x. Then, back at your command line type
> source ~/.bashrc. Now your alias should be permanent.
Solution 3 - Python
To change Python 3.6.8 as the default in Ubuntu 18.04 to Python 3.7.
Install Python 3.7
Steps to install Python3.7 and configure it as the default interpreter.
-
Install the python3.7 package using apt-get
sudo apt-get install python3.7 -
Add Python3.6 & Python 3.7 to
update-alternatives
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.6 1
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.7 2
-
Update Python 3 to point to Python 3.7
sudo update-alternatives --config python3Enter 2 for Python 3.7 -
Test the version of python
python3 --version
Python 3.7.1
Solution 4 - Python
If you have Ubuntu 20.04 LTS (Focal Fossa) you can install python-is-python3:
sudo apt install python-is-python3
which replaces the symlink in /usr/bin/python to point to /usr/bin/python3.
Solution 5 - Python
To change to python3, you can use the following command in terminal alias python=python3.
Solution 6 - Python
A simple safe way would be to use an alias. Place this into ~/.bashrc file: if you have gedit editor use
> gedit ~/.bashrc
to go into the bashrc file and then at the top of the bashrc file make the following change.
> alias python=python3
After adding the above in the file. run the below command
> source ~/.bash_aliases or source ~/.bashrc
example:
> $ python --version
>
> Python 2.7.6
>
> $ python3 --version
>
> Python 3.4.3
>
> $ alias python=python3
>
> $ python --version
>
> Python 3.4.3
Solution 7 - Python
Just follow these steps to help change the default python to the newly upgrade python version. Worked well for me.
sudo apt-install python3.7Install the latest version of python you wantcd /usr/binEnter the root directory where python is installedsudo unlink pythonorsudo unlink python3. Unlink the current default pythonsudo ln -sv /usr/bin/python3.7 pythonLink the new downloaded python versionpython --versionCheck the new python version and you're good to go
Solution 8 - Python
Update:
Since Ubuntu 20.04, the python3 is the default version, but still, python is not registered as python3 by default. In order to make that happen, you can simply do :
sudo apt install python-is-python3
For more information you can check this out.
Old way:
Do
cd ~
gedit .bash_aliases
then write either
alias python=python3
or
alias python='/usr/bin/python3'
Save the file, close the terminal and open it again.
You should be fine now! Link
Solution 9 - Python
At First Install python3 and pip3
sudo apt-get install python3 python3-pip
then in your terminal run
alias python=python3
Check the version of python in your machine.
python --version
Solution 10 - Python
As an added extra, you can add an alias for pip as well (in .bashrc or bash_aliases):
> alias pip='pip3'
You many find that a clean install of python3 actually points to python3.x so you may need:
>alias pip='pip3.6'
>alias python='python3.6'
Solution 11 - Python
This is a simple way that works for me.
sudo ln -s /usr/bin/python3 /usr/bin/python
You could change /usr/bin/python3 for your path to python3 (or the version you want).
But keep in mind that update-alternatives is probably the best choice.
Solution 12 - Python
As it says, update-alternatives --install needs <link> <name> <path> and <priority> arguments.
You have link (/usr/bin/python), name (python), and path (/usr/bin/python3), you're missing priority.
update-alternatives --help says:
> <priority> is an integer; options with higher numbers have higher priority in automatic mode.
So just put a 100 or something at the end
Solution 13 - Python
get python path from
ls /usr/bin/python*
then set your python version
alias python="/usr/bin/python3"
Solution 14 - Python
To change Python 3.6.8 as the default in Ubuntu 18.04 from Python 2.7 you can try the command line tool update-alternatives.
sudo update-alternatives --config python
If you get the error "no alternatives for python" then set up an alternative yourself with the following command:
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 2
Change the path /usr/bin/python3 to your desired python version accordingly.
The last argument specified it priority means, if no manual alternative selection is made the alternative with the highest priority number will be set. In our case we have set a priority 2 for /usr/bin/python3.6.8 and as a result the /usr/bin/python3.6.8 was set as default python version automatically by update-alternatives command.
we can anytime switch between the above listed python alternative versions using below command and entering a selection number:
update-alternatives --config python
Solution 15 - Python
For another non-invasive, current-user only approach:
# First, make $HOME/bin, which will be automatically added to user's PATH
mkdir -p ~/bin
# make link actual python binaries
ln -s $(which python3) python
ln -s $(which pip3) pip
python pip will be ready in a new shell.
Solution 16 - Python
Simply remove python-is-python2:
sudo apt purge python-is-python2
And install python-is-python3:
sudo apt install python-is-python3
It will automate the process of transition to new python3. Optionally you can get rid of remaining packages later:
sudo apt autoremove && sudo apt autoclean
Solution 17 - Python
Set priority for default python in Linux terminal by adding this:
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 10
sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 1
Here, we set python3 to have priority 10 and python2 to priority 1. This will make python3 the default python. If you want Python2 as default then make a priority of python2 higher then python3
Solution 18 - Python
~$ sudo apt-get install python3.9
/usr/bin$ cd /usr/bin
/usr/bin$ sudo unlink python3
/usr/bin$ sudo ln -sv /usr/bin/python3.9 python3
/usr/bin$ python3 --version
Python 3.9.5
/usr/bin$ pip3 --version
pip 20.0.2 from /usr/lib/python3/dist-packages/pip (python 3.9)
Solution 19 - Python
The best way in ubuntu 18.04 which will work for all users is
sudo vim /etc/bash.bashrc
add lines
alias python=python3
alias pip=pip3
Save the changes and restart .
After restart what ever version of python 3 you have in the system along with python 2.7 will be taken as default. You could be more specific by saying the following in alias if you have multiple version of python 3.
sudo vim /etc/bash.bashrc
add lines
alias python=python3.6
alias pip=pip3.6
Solution 20 - Python
sudo rm /usr/bin/python3 #remove existing link
sudo ln /usr/bin/python3.8 /usr/bin/python3 # create a new link to the version of your choice
Solution 21 - Python
You didn't include the priority argument
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 5
You can replace 5 with any priority you want. A higher priority alternative takes precedence over lower priority.
Solution 22 - Python
If there is a possibility to use particular python version directly, I would go for it compared to update-alternatives and alias solution.
Ex.
python3.6 -m pip install pytest
ptyhon3.6 -m pytest test_sample.py
-m executes particular module for that particular python version.
The first line will install pytest for for that particular version and user in possible location /home/user/.local/lib/python3.5/site-packages
Solution 23 - Python
in my case it happened when i run this command in my terminal " alias python=python3 "
Solution 24 - Python
At first, Make sure Python3 is installed on your computer
Go to your terminal and type:
cd ~/ to go to your home directory
If you didn't set up your .bash_profile yet, type touch .bash_profile to create your .bash_profile.
Or, type open -e .bash_profile to edit the file.
Copy and save alias python=python3 in the .bash_profile.
Close and reopen your Terminal. Then type the following command to check if Python3 is your default version now:
python --version
You should see python 3.x.y is your default version.
Cheers!