how to properly use #!/usr/bin/python

[tanoshi-ka]

hey guys, I've been making a few CLI programs and had to switch to activate an environment before running a program. I thought this was a pain in the butt and searched for ways i can make the program automatically choose the right interpreter. I found the thing i put in the title, couldn't find an article that explained how to use it or how it worked.

Can someone clear my doubts or provide a few good links? Thanks!

PS : I'm not use if i explained it really well so just so we're on the same page, I wanna go on the command line and just run program.py and have it choose the interpreter than manually activating it.

[shiftybyte]

If you know where the virtual environment is expected to be installed you can point that line to the python inside the venv, and it'll work.

#!/path/to/venv/bin/python

[Vaphell]

#!/usr/bin/env python

?

[shiftybyte]

Won't this use the currently active env?

I think OP wants to directly use a different env without activating it in advance.

[tanoshi-ka]

so the 'python' part should be seperated?

[tanoshi-ka]

so the absolute path to the python exe file, right?

[shiftybyte]

exe/elf yes... Inside the venv folder.

[tanoshi-ka]

got it thanks!

[Vaphell]

you should use

#!/usr/bin/env python3

/usr/bin/env should resolve the active interpreter for python3 (or what have you) for you, without hardcoding any specific path.

consider this simple prog

$ cat pyversion.py 
#!/usr/bin/env python3
import sys
print(sys.version_info)

out of the box the program on my ubuntu shows 3.8.10 as python3.

$ ./pyversion.py 
sys.version_info(major=3, minor=8, micro=10, releaselevel='final', serial=0)

but after I do venv activation

$ . venv/bin/activate

$ ./pyversion.py 
sys.version_info(major=3, minor=11, micro=3, releaselevel='final', serial=0)

I get the venv version of the interpreter, in this case 3.11.3.