How to execute a Python3 script from Bash, in the shorthand fashion?

Question

I'm converting all my Python2 scripts to work with Python3.

From within a bash wrapper, scripts can be executed with Python3 with:

python3 myScript.py

However, I have an old wrapper which called a Python2 script via the shorthand, i.e

./myScript.py

How do I ensure that this shorthand will run the script with Python3 by default?

The server these scripts are running on is Ubuntu 14.04.

score 2 · Accepted Answer · answered Nov 25 '19 at 14:19

2

You can use the "hash-bang" #!/usr/bin/python3

answered Nov 25 '19 at 14:19

redhatvicky

1,876
7
8

I think you mean "she-bang", and the preferred way to do it would be `#!/usr/bin/env python` since not every distribution will have python in that location (for example NixOS) – SitiSchu Nov 25 '19 at 14:27
Yeah depends on the unix Flavors she-bang/hash-bangs.https://www.in-ulm.de/~mascheck/various/shebang/ – redhatvicky Nov 25 '19 at 14:31

score 0 · Answer 2 · answered Nov 25 '19 at 14:22

0

more information regarding your operating system would be helpful. If you are on linux or mac you can add the following to the first line of your script:

#!/usr/local/bin/python

adjusting for the location of your python3. Then you could change the file to executable using:

chmod u+x script

After this you would be able to run your script with just

script

answered Nov 25 '19 at 14:22

Doug Federman

11
2

Added OS info in description – x3nr0s Nov 25 '19 at 14:23
You can use `#!/usr/bin/env python` to avoid hardcoding the location of the python interpreter. – SitiSchu Nov 25 '19 at 14:28
@SitiSchu, wouldn't that end up hard coding your python interpreter to what is in /usr/bin/env? – Kelvin Nov 25 '19 at 14:29
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@Kelvin note the space, it runs `/usr/bin/env` with `python` as argument. `env` will run the first python it finds in your `$PATH`. More info here: https://stackoverflow.com/a/2429517/7228176 – SitiSchu Nov 25 '19 at 14:30
on my Mac it requires /usr/bin/env python3 for this to work – Doug Federman Nov 25 '19 at 14:49
@Sitischu, neat! I like it – Kelvin Dec 17 '19 at 21:39

How to execute a Python3 script from Bash, in the shorthand fashion?

2 Answers2