PYTHON

if name == main

# The code in this 'if' statement runs only if current file is the
# the main file. Mean this 'if statement' code will not run if you import
# that file into other program.

if __name__ == '__main__':

What does if __name_=="_main__": do?

# Suppose this is foo.py.

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")

What does if __name_=="_main__": do?

basically,   (__name__ == '__main__') ==True

confirms file is NOT a/part of a module and may continue execution  

if __name__="__main__":

# Suppose this is foo.py.

print("before import")
import math

print("before function_a")
def function_a():
    print("Function A")

print("before function_b")
def function_b():
    print("Function B {}".format(math.sqrt(100)))

print("before __name__ guard")
if __name__ == '__main__':
    function_a()
    function_b()
print("after __name__ guard")