Special behavior of main function in import statement

Say first conclusion , import module Will be executed module Function level code , But if it's time to module There is main function , They don't execute .
It sounds complicated , Just look at the code below , There are also some problems that have not been solved , I hope the boss will teach

test_02.py

from test_03 import test_print

x = None
print 'test_02 execute'


def get_x():
	global x
	print 'get_X'
	return x


def set_x():
	global x
	print 'set_x'
	x = 10


if __name__ == '__main__':
	print 'execute main'
	set_x()
	print get_x()
	print '===================================='
	test_print()

test_03.py

def test_print():
	import test_02 as x
	print x.x

above test_02 perform , Called test_03 Medium test_print(), test_print To print test_02 Global variable in x, But I found that it was still the default , Why is that ?
Look at the printout

Turned out to be test_03 In the implementation of import At the time of statement , Yes test_02 Function level statements in , And if we change the code again , add id, to glance at :
test_02

if __name__ == '__main__':
	print 'execute main'
	set_x()
	print get_x()
	print '===================================='
	test_print()
	print get_x()
	print id(x)

test_03

def test_print():
	from test_02 import x
	print x
	print id(x)

Execution results

We found that id Is not the same
in other words test_03 in import x It was not only implemented once test_02 The code in , Not even the same object
But if we put set_x() from main Function to the outside , Look at the results again

id It's the same again , Why is that ? Do you have a boss to explain main Why is function so special