Detect whether package is being run as a program within __init__.py

I have a Python package with an __init__.py that imports some things to be exposed as the package API.

# __init__.py

from .mymodule import MyClass
# ...

I also want to be able to use the package as a command-line application, as in python -m mypackage, so I have a __main__.py file for that purpose:

# __main__.py

if __name__ == '__main__':
    from .main import main
    main()

So far so good. The problem is that, when the package is run as a program like this, I want to be able to do some stuff before importing any of the submodules - namely changing some environment variables before some third-party dependencies are loaded.

I do not know how to do this, at least not in a reasonable way. Ideally, I would like to do something like:

# __init__.py

def thePackageIsRunningAsAnApplication():
    # ???

def prepareEnvironment():
    # ...

if thePackageIsRunningAsAnApplication():
    prepareEnvironment()

from .mymodule import MyClass
# ...

The problem is I don't think thePackageIsRunningAsAnApplication() can be implemented. The usual __name__ == '__main__' does not work here, because the main module being run is __main__.py, not __init__.py. In fact, I would prefer to define and run prepareEnvironment within __main__.py, but I don't know how to get that to run before the inner modules are loaded by __init__.py.

I might (not sure, actually) work around it by lazily loading dependencies on my module, or somehow delaying the internal module loading or something, but I would prefer to avoid doing something like that just for this.

EDIT: Thinking more about it, lazy loading probably would not work either. In the example, MyClass is, well, a class, not a submodule, so I cannot lazily load it. Moreover, MyClass happens to inherit from a class from that third-party dependency I was mentioning, so I cannot even define it without loading it.

source https://stackoverflow.com/questions/72262763/detect-whether-package-is-being-run-as-a-program-within-init-py