Conditional check

Definitely a good question/answer to know for a potential interview. I recommend you set up a couple of python modules to test this out. People who are primarily JavaScript or PHP programmers might get tripped up, but a Pythonista will smile and tell them:

• __name__ (aka dunder name) is a special variable which holds the identity of the module being executed.

• __main__ is a string VALUE that __name__ takes on ONLY if it is the was the file executed. Otherwise, it will have the name of the module/import.

Often the statement at the end of a main app module will have the following conditional block:

if __name__ == '__main__':
    # execute the block ONLY if this is the main module.
    execute_the_app()

I recommend you try this experiment...

Suppose we had two modules, one called "app.py", the other called "module.py". app.py will be the one we run with Python and module will run when it is imported by app.py

app.py

import module
print("Hello from app.py")
print("app.py reports its name: ", __name__)

module.py

print("Hello from module.py")
print("module.py reports its name:  ", __name__)

Then we finally run the file (with Python 3)

treehouse:~/workspace$ python app.py                                                      
Hello from module.py                                                                      
module.py reports its name:  module                                                       
Hello from app.py                                                                         
app.py reports its name:  __main__   

When programming you can isolate some code in a module and ONLY run it when it is the main executable module, and not run it when it is a support module. Good luck with your Python journey!