running python 2 vs 3

Terry Reedy tjreedy at udel.edu
Thu Mar 20 23:05:49 CET 2014


On 3/20/2014 3:07 PM, John Gordon wrote:

> There are two ways (at least!) to run a python script:
>
> 1. Execute the python interpreter manually, supplying the python script name
>     as an arugment, like so:
>
>       python myscript.py
>       python2 otherscript.py
>       python3 yetanotherscript.py
>
> This lets you choose on-the-fly which version of python is being used to
> interpret the script.
>
> 2. Execute the python script directly by just typing its name, like so:
>
>       myscript.py
>       ./otherscript.py
>       /other/directory/yetanotherscript.py
>
>     Depending on your operating system, this may require:
>       a. Permissions on the script file be set to allow execution;
>       b. A 'shebang' entry as the first line in the file which specifies the
>          program that shall be executed;

         c. An association between '.py' and some version of python.

3. Use the python launcher py.exe with version selection.
     py -2 myscript.py
     py -3 myscript.py

As far as I know, this is only for Windows at present.

-- 
Terry Jan Reedy




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