def functionA():
print("a1")
from foo2 import functionB
print("a2")
functionB()
print("a3")
print("before import")
import math
print("before functionA")
def functionA():
print("Function A")
print("before functionB")
def functionB():
print("Function B {}".format(math.sqrt(100)))
print("before __name__ guard")
if __name__ == '__main__':
functionA()
functionB()
print("after __name__ guard")
'''
Special Variables
When the Python interpeter reads a source file, it first defines a few special variables. In this case, we care about the __name__ variable.
When Your Module Is the Main Program
If you are running your module (the source file) as the main program, e.g.
python foo.py
the interpreter will assign the hard-coded string "__main__" to the __name__ variable, i.e.
# It's as if the interpreter inserts this at the top
# of your module when run as the main program.