Update python on linux 2.7 to 3.5

Question

So I updated python using these instructions:

sudo apt-get install build-essential checkinstall
sudo apt-get install libreadline-gplv2-dev libncursesw5-dev libssl-devlibsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev

then

cd ~/Downloads 
wget https://www.python.org/ftp/python/3.5.0/Python-3.5.0.tgz
tar -xvf Python-3.5.0.tgz
cd Python-3.5.0

then

./configure
sudo make install



python3.5
Python 3.5.0 (default, Oct  3 2015, 03:16:42) 
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

and it worked but when I closed terminal, and wrote python -v it is still python 2.7 and still getting errors executing code that use v3+ standard libraries

How to make it working as 3.5?

Solution 1

You still have Python 2 installed, and the python command is still set up to invoke that version by default. Try running your scripts like this:

python3 yourscriptname.py

In /usr/bin/, "python" is actually a symlink to python2.7. If you'd rather not have to type the 3 at the end whenever you use python, change that symlink to point to python3 instead. Then python will run Python 3.5 and you can use python2.7 or just python2 to run Python 2.7 scripts.

EDIT: Alternatively, you could put alias python=python3 in your ~/.bashrc file to do the same thing, but without needing root access and for your user account only.

Solution 2

//install python 3.6

sudo add-apt-repository ppa:jonathonf/python-3.6
sudo apt update
sudo apt install python3.6

//change default python

sudo rm /usr/bin/python
sudo ln -s /usr/bin/python3 /usr/bin/python

//view default

 python -V

Solution 3

You might just have destroyed your system python installation by doing

sudo make install

This installs in the default path! And will possibly overwrite anything your linux distro has there to work correctly. Never do sudo make installs if you're not sure where the resulting stuff goes. In case of Python, you should have done

sudo make altinstall

to have it installed next to the default python but the best thing is to install and use the python version via your distro's package manager.

Solution 4

I read that changing global python to 3.5 can cause some problems so I set build commands in geany for python3 and I can still run scripts outside by typing python3 xxx.py and it's comfortable now

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Comments

[Budi Mulyo]

just write in terminal alias python=python3 from askubuntu.com/questions/320996/…

[Dylan Craine]

@BudiMulyo If you add an alias via the terminal like that, it'll only last until you log out. It's probably better to add your alias to something like ~/.bashrc so that it'll be persistent. Nevertheless, it's a good idea - I'll add it to the answer.