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Calling a python Command-line tool with arguments, with PythonKit using Swift

June 7, 2022

I have been experimenting a bit with PythonKit and have some simple examples working. However I would now like to call a python script that takes some command line arguments and I can’t seem to get it working – it mostly just crashes.

This is the code I am using in swift – I am trying to get the version number of the script:

let sys = Python.import("sys")
sys.path.append(“/Path/To/Script/Directory/“)
var example = Python.import(“my_script”)

example.main("-v")

If I call the script like so: example.main() – without any arguments at all, the script prints out its arguments:

optional arguments:
    -v, --version         show program's version number and exit
    -H, --help            Display this information
    etc.

But PythonKit then crashes in:

@discardableResult
    func dynamicallyCall(
        withArguments args: [PythonConvertible] = []) -> PythonObject {
        return try! throwing.dynamicallyCall(withArguments: args)
    }

The crash seems to be caused by a call to sys.exit(0) in the python script just after the argument list is printed, when there are no arguments. The script works normally if I use it in the terminal.

So, can someone tell me how to call a python script that expects arguments, from PythonKit?

Also, is there something that I could do to prevent a crash if there are no arguments?

>Solution :

I’m not familiar with swift but know that python getting arguments from sys.argv list

So how about try to add arguments directly into sys object:

let sys = Python.import("sys")
sys.path.append(“/Path/To/Script/Directory/“)
sys.argv.append("-v")
var example = Python.import(“my_script”)
example.main()