modules

mod1.py

if __name__ == '__main__':
    print('mod1 is executing by having been called directly')
else:
    print('mod1 is executing by having been imported by module ' + __name__)

def f():
    if __name__ == '__main__':
        print('mod1.f is executing from module mod1')
    else:
        print('mod1.f is executing from module' + __name__)

f()

# > python mod1.py
# mod1 is executing by having been called directly
# mod1.f is executing from mod1

mod2.py

from mod1 import f
f()

# > python mod2.py
# mod1 is executing by having been imported by module mod1
# mod1.f is executing from module mod1
# mod1.f is executing from module mod1