🔒 Someon explain me the if name == main

[whole dove]

Someon explain me the if name == main

[left dome]

@whole dove

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[fierce fern]

!ifmain

[left dome]

`if __name__ == '__main__'`

This is a statement that is only true if the module (your source code) it appears in is being run directly, as opposed to being imported into another module. When you run your module, the __name__ special variable is automatically set to the string '__main__'. Conversely, when you import that same module into a different one, and run that, __name__ is instead set to the filename of your module minus the .py extension.

Example

# foo.py

print('spam')

if __name__ == '__main__':
    print('eggs')

If you run the above module foo.py directly, both 'spam'and 'eggs' will be printed. Now consider this next example:

# bar.py

import foo

If you run this module named bar.py, it will execute the code in foo.py. First it will print 'spam', and then the if statement will fail, because __name__ will now be the string 'foo'.

Why would I do this?

• Your module is a library, but also has a special case where it can be run directly
• Your module is a library and you want to safeguard it against people running it directly (like what pip does)
• Your module is the main program, but has unit tests and the testing framework works by importing your module, and you want to avoid having your main code run during the test

[solemn pawn]

it prevents the code from running when you import it as a module

so you can have different behaviors between running python myscript.py and python some_otherscript.py where some_otherscript.py imports myscript

[whole dove]

can code example

[solemn pawn]

there's one here

[whole dove]

I can run it?

from kivy.app import App

class Myapp(App):
    pass


if __name__ == '__main__':
    Myapp().run()

if I try in other file
I can do

Myapp().run()

you mean if I make a file and named it a.py
and writed

print("aaA")

when import it on other file like b.py

import a

when run b.py I will get aaA ?

@solemn pawn

but If I use ifmain I don't will get anything right?

[fierce fern]

it is also important for multiprocessing (which runs your file multiple times, doing different things in each run), so that Python knows what to run in the main process versus what to run in the helpers

[whole dove]

its my explain correct in the top?

I didn't learn mp yet

[fierce fern]

This will print foo if you run foo.py or bar.py: ```py

foo.py

print("foo")

bar.py

import foo

This will still print if you run `foo.py`, but not if you run `bar.py`:
```py
# foo.py
if __name__ == "__main__":
    print("foo")

# bar.py
import foo

[whole dove]

I understand

[fierce fern]

I'm not sure about Kivy but sometimes when working with libraries, you may run commands like py -m kivy main.py MyApp instead of running directly py main.py, in which case Kivy will import your file and run your app in a way different from you calling MyApp().run() yourself

[whole dove]

from kivy.app import App

class Myapp(App):
    pass


if __name__ == '__main__':
    Myapp().run()

we can do Myapp().run() in other file? so we runned this? and ifmain didn't blocked that?

@fierce fern

also can you explain me the if __name__ == '__main__'

also what main doesn

[fierce fern]

pretty much, you could do something like ```py
from main import Myapp

maybe create with custom configs

app = Myapp(configs=...)

don't even run(), just call something to test

app.test_xyz()

run, optionally with other configs

app.run(xyz=123)

[fierce fern]

it is just a special name

[whole dove]

💀

[brittle lark]

for this example u could make it to import as a blueprint but run as an app

[fierce fern]

no real meaning, just what's used

a bit like why is import called import - it could be called something else, it just is what it is

[whole dove]

ok

[left dome]

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