Change the "default" Python by putting it ahead of the system Python on your path, for instance:
export PATH=/usr/local/bin:$PATH
In my case, on my Mac OSX, with Python 2.7.18 installed via mac ports, I was able to set the python version to 2.7 with:
$ sudo port select --set python python27
So:
$ python -V
Python 2.7.18
Do right thing, do thing right!
--->Zero Open your terminal,
--Firstly input python -V
, It likely shows:
Python 2.7.10
-Secondly input python3 -V
, It likely shows:
Python 3.7.2
--Thirdly input where python
or which python
, It likely shows:
/usr/bin/python
---Fourthly input where python3
or which python3
, It likely shows:
/usr/local/bin/python3
--Fifthly add the following line at the bottom of your PATH environment variable file in ~/.profile file or ~/.bash_profile
under Bash or ~/.zshrc
under zsh.
alias python='/usr/local/bin/python3'
OR
alias python=python3
-Sixthly input source ~/.bash_profile
under Bash or source ~/.zshrc
under zsh.
--Seventhly Quit the terminal.
---Eighthly Open your terminal, and input python -V
, It likely shows:
Python 3.7.2
I had done successfully try it.
Others, the ~/.bash_profile
under zsh is not that ~/.bash_profile
.
The PATH environment variable under zsh instead ~/.profile
(or ~/.bash_file
) via ~/.zshrc
.
Help you guys!
Old question, but alternatively:
virtualenv --python=python3.5 .venv
source .venv/bin/activate
Check the location of python 3
$ which python3
/usr/local/bin/python3
Write alias in bash_profile
vi ~/.bash_profile
alias python='/usr/local/bin/python3'
Reload bash_profile
source ~/.bash_profile
Confirm python command
$ python --version
Python 3.6.5
According to a quick google search, this update only applies to the current shell you have open. It can probably be fixed by typing python3, as mac and linux are similar enough for things like this to coincide. Link to the result of google search.
Also, as ninjagecko stated, most programs have not been updated to 3.x yet, so having the default python as 3.x would break many python scripts used in applications.
On Mac OS X using the python.org installer as you apparently have, you need to invoke Python 3 with python3
, not python
. That is currently reserved for Python 2 versions. You could also use python3.2
to specifically invoke that version.
$ which python
/usr/bin/python
$ which python3
/Library/Frameworks/Python.framework/Versions/3.2/bin/python3
$ cd /Library/Frameworks/Python.framework/Versions/3.2/bin/
$ ls -l
total 384
lrwxr-xr-x 1 root admin 8 Apr 28 15:51 2to3@ -> 2to3-3.2
-rwxrwxr-x 1 root admin 140 Feb 20 11:14 2to3-3.2*
lrwxr-xr-x 1 root admin 7 Apr 28 15:51 idle3@ -> idle3.2
-rwxrwxr-x 1 root admin 138 Feb 20 11:14 idle3.2*
lrwxr-xr-x 1 root admin 8 Apr 28 15:51 pydoc3@ -> pydoc3.2
-rwxrwxr-x 1 root admin 123 Feb 20 11:14 pydoc3.2*
-rwxrwxr-x 2 root admin 25624 Feb 20 11:14 python3*
lrwxr-xr-x 1 root admin 12 Apr 28 15:51 python3-32@ -> python3.2-32
lrwxr-xr-x 1 root admin 16 Apr 28 15:51 python3-config@ -> python3.2-config
-rwxrwxr-x 2 root admin 25624 Feb 20 11:14 python3.2*
-rwxrwxr-x 1 root admin 13964 Feb 20 11:14 python3.2-32*
lrwxr-xr-x 1 root admin 17 Apr 28 15:51 python3.2-config@ -> python3.2m-config
-rwxrwxr-x 1 root admin 25784 Feb 20 11:14 python3.2m*
-rwxrwxr-x 1 root admin 1865 Feb 20 11:14 python3.2m-config*
lrwxr-xr-x 1 root admin 10 Apr 28 15:51 pythonw3@ -> pythonw3.2
lrwxr-xr-x 1 root admin 13 Apr 28 15:51 pythonw3-32@ -> pythonw3.2-32
-rwxrwxr-x 1 root admin 25624 Feb 20 11:14 pythonw3.2*
-rwxrwxr-x 1 root admin 13964 Feb 20 11:14 pythonw3.2-32*
If you also installed a Python 2 from python.org, it would have a similar framework bin directory with no overlapping file names (except for 2to3).
$ open /Applications/Python\ 2.7/Update\ Shell\ Profile.command
$ sh -l
$ echo $PATH
/Library/Frameworks/Python.framework/Versions/2.7/bin:/Library/Frameworks/Python.framework/Versions/3.2/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin
$ which python3
/Library/Frameworks/Python.framework/Versions/3.2/bin/python3
$ which python
/Library/Frameworks/Python.framework/Versions/2.7/bin/python
$ cd /Library/Frameworks/Python.framework/Versions/2.7/bin
$ ls -l
total 288
-rwxrwxr-x 1 root admin 150 Jul 3 2010 2to3*
lrwxr-x--- 1 root admin 7 Nov 8 23:14 idle@ -> idle2.7
-rwxrwxr-x 1 root admin 138 Jul 3 2010 idle2.7*
lrwxr-x--- 1 root admin 8 Nov 8 23:14 pydoc@ -> pydoc2.7
-rwxrwxr-x 1 root admin 123 Jul 3 2010 pydoc2.7*
lrwxr-x--- 1 root admin 9 Nov 8 23:14 python@ -> python2.7
lrwxr-x--- 1 root admin 16 Nov 8 23:14 python-config@ -> python2.7-config
-rwxrwxr-x 1 root admin 33764 Jul 3 2010 python2.7*
-rwxrwxr-x 1 root admin 1663 Jul 3 2010 python2.7-config*
lrwxr-x--- 1 root admin 10 Nov 8 23:14 pythonw@ -> pythonw2.7
-rwxrwxr-x 1 root admin 33764 Jul 3 2010 pythonw2.7*
lrwxr-x--- 1 root admin 11 Nov 8 23:14 smtpd.py@ -> smtpd2.7.py
-rwxrwxr-x 1 root admin 18272 Jul 3 2010 smtpd2.7.py*
Set Python 3.5 with higher priority
sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.5 2
Check the result
sudo update-alternatives --config python
python -V
Navigate to:
My Computer -> Properties -> Advanced -> Environment Variables -> System Variables
Suppose you had already having python 2.7 added in path variable and you want to change default path to python 3.x
then add path of python3.5.x folder before python2.7 path.
open cmd: type "python --version"
python version will be changed to python 3.5.x
Check the execution path of python3 where it has libraries
$ which python3
/usr/local/bin/python3 some OS might have /usr/bin/python3
open bash_profile file and add an alias
vi ~/.bash_profile
alias python='/usr/local/bin/python3' or alias python='/usr/bin/python3'
Reload bash_profile to take effect of modifications
source ~/.bash_profile
Run python command and check whether it's getting loading with python3
$ python --version
Python 3.6.5
In short: change the path in Environment Variables!
For Windows:
Advanced System Settings > Advance (tab)
. On bottom you'll find 'Environment Variables'
Double-click on the Path
. You'll see path to one of the python installations, change that to path of your desired version.
I am using OS X 10.7.5 and Python 3.4.2. If you type python3
and what you want to run it will run it using python 3. For example
pyhton3 test001.py
. That ran a test program I made called test001. I hope this helps.
sudo mv /usr/bin/python /usr/bin/python2
sudo ln -s $(which python3) /usr/bin/python
This will break scripts, but is exactly the way to change python. You should also rewrite the scripts to not assume python
is 2.x. This will work regardless of the place where you call system
or exec
.
Source: Stackoverflow.com