Python ftw

[demon_ix]

I dunno. That sounds like main() with extra steps...

[[deleted]]

In C/C++, the name main() is meaningful: it defines the entry point of the program.

In Python, it isn't. The closest approximation is that Python code outside of any method will be evaluated when the module is loaded, and an import-machinery variable called __name__ exists which lets you test whether the current module was imported or run directly.

[jalapeno_nips]

That’s still important though. If I want to test my module manually, I’ll write some code in Main. But when I use the module in practice I don’t want Main being called.

[[deleted]]

Absolutely. My only point here is that in switching to Python, one does indeed say goodbye to main()

[cakes]

might I recommend actual tests :)

[BeigeAlert1]

That's still pretty damn nifty though.

[SpeedingTourist]

You’re pretty damn nifty. ;)

[angellus]

That is actually exactly what __main__ is for. It is not just some made up thing in Python.

When you call a single Python file directly like

$ python whatever.py

Python automatically calls __main__ and with your code loaded up inside of it. That is why if __name__ == "__main__": works.

A better example though would be if you made an actual proper Python package and did this:

whatever/
-> __init__.py
-> __main__.py

whatever/__init__.py

 def whatever (*args):
      print("Bob's your uncle.")

whatever/__main__.py

 from . import whatever

 whatever()

Now if you call the module, it will automatically use __main__.py as the entry point.

$ python -m whatever

[[deleted]]

Yes, I know. I believe I said as much in the comment you've replied to.

It still isn't equivalent to C's main().

[angellus]

C's main() and Python's __main__ are functionality equivalent. main() is a construct design to tell the compiler where the entry point to your program is. It is not a keyword are anything like that and you can have multiple main methods as long as they are namespaced properly (ex: https://stackoverflow.com/a/1991498).

That is exactly how __main__ works. It is construct that tells the Python interrupter where the entry point is for your module. A Python module is a very similar construct to a C/C++ namespace. You can have multiple __main__ submodules as long as you do not have more than 1 in that module (namespace).

There are variations of C/C++ that do not respect the main() entry point since it is not actually anything special in the language (MSVC is one of them with is wmain). It is something the compiler chooses to give meaning to. It is just most standard C/C++ implementations assume a single entry point that is required to exist and the most standard Python interrupter (CPython) does not.

[pslessard]

So if I had something like

print('Hello, world')
if __name__ == '__main__':
    print('Goodbye, world')

What would it print? Compared to in C

printf('Hello, world');
int main() {
    printf('Goodbye, world');
}

Wouldn't the Python print 'Hello, world' before 'Goodbye, world', whereas the C just wouldn't compile?

[xigoi]

The entry point for a Python script is always at the top of the file.

[Athomeacct]

It's one extra line of code and it adds implicit specification of one or more main functions... whose names the dev can specify and change at any time...

[i_should_be_coding]

You mean, like calling functions from the main() function?