Python中这段代码的意思没看懂，求助

stackoverflow 上关于 What will happen if two modules import each other? 的讨论

https://stackoverflow.com/questions/744373/circular-or-cyclic-imports-in-python

这一段没看懂，哪个是哪个看晕了：

Finally, the executing script runs in a module named __main__, importing the script under its own name will create a new module unrelated to __main__.

例子

# first.py
from second import b
def a():
print(‘This is a’)

# second.py
from first import a

def b():
    print('This is b')

执行 second.py