CODEWITHSUNDEEP
pythondebugging
Ali_Waris
Ali_Waris

Reputation: 2382

How to find out the starting point of code execution in any Python project?

I have been looking at various open source GitHub Python projects like, http-prompt and Theano

What I am not able to figure out is where their starting points are, so that I can debug them gracefully. Do I need to look in each and every file for the __main__ method?

I am from Android background; so I was searching something related like AndroidManifest.xml from where I can get an idea as where the code is getting started, but I was unsuccessful in my attempts.

Upvotes: 4

Views: 7863

Answers (2)

Nicolas Cornette
Nicolas Cornette

Reputation: 782

There are two ways a Python script can be loaded:

  • By import : import mymodule
  • By commandline : $ python mymodule.py

In both cases all code inside the script is executed

Usually if __name__ == '__main__': defines the entry point : 

if __name__ == '__main__': 
    print('Started from commandline')
else:
    print('Imported as a module')

In a git project, you can try this to find all scripts made to be launched from command-line : 

$ git grep "if __name__ ?== ?\W__main__\W"

Note that the project you mentioned, doesn't contain any explicitly defined entry point, instead the entry point script is generated at packaging time for distribution (see setup.py for this purpose)

Upvotes: 9

jonrsharpe
jonrsharpe

Reputation: 122007

The Python equivalent of a manifest file is generally setup.py, so this is a good place to start looking. A package can:

If neither of these is provided, the package is probably designed to be imported rather than executed, in which case take a look at the usage examples along with the root __init__.py (e.g. Theano's), which will probably tell you what objects are exposed to the outside world. See the Python docs for more information on module structure.

However, Python is a dynamic, flexible language so there's no "magic bullet" to tell you where to look; there isn't e.g. a specific main.py file that must be defined, for example (although there is a __main__.py that can be defined, see What is __main__.py?)

Upvotes: 3

Related Questions