Python3作为默认python版本

Question

I am creating a script that will call an API and return some results. I have the script working with pycharm on my computer but I am running into a few problems but I want to focus on this problem first.

1) I am unable to set Python3 as my default python.

I am using a Mac. When I go into terminal I enter $ python --version and it returns Python 2.7.10

I then enter $ alias python=python3 , and when I run $python --version it returns Python 3.7.2

When I create a py.script with the os module, it does not work. See my code below.

import os
os.system('alias python=python3')
print(os.system('python --version')

It prints 2.7.10

I also tried to run the os.system('alias python="python3"')

Answer 1

On -nix machines (including OSX), one way to change the version of the interpreter that the script runs with is to add a shebang as the first line of your script.

Eg.

#! /usr/bin/env python3

import sys
print(sys.version)

Then to run your script do:

~/$ chmod u+x myscript.py
~/$ ./myscript.py 

You only need to run the chmod command the first time. It enables you to execute the file. Whenever you run your script directly (rather than as an argument to python) your script will be run using the version specified by the shebang.

Answer 2

welcome to SO! Pycharm needs you to specify which interpreter to use as default, as it wouldn't choose the system one by default.

So if you want python3 , you can run which python3 , and use the path as a settings for the current project. How to do that step by step is here:

https://www.jetbrains.com/help/pycharm/configuring-python-interpreter.html

Hope it help, post a comment if you need more details.

Answer 3

This isn't surprising, because os.system opens its own shell, and running alias in that way only affects the currently running terminal. Each call to os.system would be in a separate shell.

I'm not sure what your ultimate goal is, but you almost certainly don't need to change what python means to a shell to do it. If you DO, you'll have to run both commands at once.

import subprocess

cp = subprocess.run("alias python=python3 && /path/to/script")

Answer 4

Interesting - apparently os.system ignores the alias? Just checked it in Linux and got the same results.

Try sys instead of os :

import sys
print(sys.version)