How to update Python 2.7 to 3 in terminal

Question

I'm trying to run a python3 script through terminal on my mac, but every time I execute the file terminal uses Python 2.7 despite 3.7 being installed.

I have read in other threads that python3 can be run by using the "python3" command, but this seems to load me into the python syntax with ">>>" at the beginning of every line

Is there a way of running python 3 while using whatever syntax is native to terminal?

Or as a last resort what is the command to run a .py file from the python syntax?

Solution 1

To run a python script from the terminal in python3 use:

python3 python-file.py

if you want to write it this way python python-file.py you have to create a symbolic link from /usr/bin/python to /usr/bin/python3 by using the command (only do this if you know what you are doing):

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

if you want to run the file using ./python-file.py you have to add a "shebang" to the top of your file:

#!/usr/bin/env python3

Solution 2

1. Install ppa

sudo add-apt-repository ppa:deadsnakes/ppa

2. Update packages

sudo apt-get update

3. Upgrade python 2.x to python 3.x

sudo apt-get install python3.6

Change default python

sudo rm /usr/bin/python

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

Check default version

python -V

Comments

[Gennady Kandaurov]

python3 a.py has to work

[Mntfr]

I think you are just typing python3 without the file name so just chage your command to python3 myprogram.py

[VPfB]

I do strongly recommend against changing /usr/bin/python from version 2 to 3 unless you know very well what you are doing. It can break many scripts.

[VPfB]

A better shebang line is #!/usr/bin/env python3.

[Thomas Savage]

This is exactly what I was asking! Thankyou

[MaxNoe]

As a side note, arch and fedora already have /usr/bin/python as python3 (Arch since ages, fedora pretty recently)