if __name__ == '__main__' python

Question

I have gone through so many articles regarding this:

if __name__ == '__main__'

But I didn't get it... I am going to share you code. What is a more brief explanation?

I have created one file, "ab.py":

def a():
    print('A function in ab file');

a()

The second file is "xy.py"

import ab

def b():
    print('b function')

def x():
    print ('s');

x()

if __name__ == "__main__" :
    b()

When I execute this code then this output is coming:

A function in ab file
s
b function

What does this mean? What is this code actually doing? Why do we implement this? Our code is also working without it.

if __name__ == "__main__":
    b()

Answer 1

You should get in the habit of using this almost always.

Anything that comes after if __name__ == '__main__': will be run only when you explicitly run your file.

python myfile.py

However, if you import myfile.py elsewhere:

import myfile

Nothing under if __name__ == '__main__': will be called.

Answer 2

A really simple example to understand this statement is the following:

Assume that we have the following Python script named: using_name.py:

---

# Filename: using_name.py

if __name__ == '__main__':
    print 'This program is being run by itself'
else:
    print 'I am being imported from another module'

---

Now, try to do the following two things and see what happens:

---

1) Run directly the script

python using_name.py

Result

This program is being run by itself

---

2) Import the script

python

import using_name

Result

I am being imported from another module