debug - Python中使用pdb调试的疑问？

Question

调试的测试程序

import pdb
import sys
def add(num1=0, num2=0):
    print('add')
    return int(num1) + int(num2)
def main():
    print(sys.argv)
    pdb.set_trace()  # 添加断点
    addition = add(sys.argv[1], sys.argv[2])
    print(addition)
if __name__ == '__main__':
    main()

注释：由于segmentfault限制了pre的height，为了可读所以分为两部分截取

使用pdb单步调试step进入add函数内部后为什么会出现两条相同的return int(num1) + int(num2)语句？

$ python test.py 1 2
['test.py', '1', '2']
> /home/testenv/test.py(9)main()
-> addition = add(sys.argv[1], sys.argv[2])

(Pdb) s  # step into add function
--Call--
> /home/testenv/test.py(3)add()
-> def add(num1=0, num2=0):

(Pdb) n
> /home/testenv/test.py(4)add()
-> print('add')

(Pdb) n
add
> /home/testenv/test.py(5)add()
-> return int(num1) + int(num2)

(Pdb) n
--Return--
> /home/testenv/test.py(5)add()->3
-> return int(num1) + int(num2)

下面也出现了两条相同的print语句，只是一条是main()，另外一条是main()->None。而且print(addition)后程序不是应该退出吗？为什么最后还要回到main才能退出？

(Pdb) n
> /home/testenv/test.py(10)main()
-> print(addition)

(Pdb) n
3
--Return--
> /home/testenv/test.py(10)main()->None
-> print(addition)

(Pdb) n
--Return--
> /home/testenv/test.py(12)<module>()->None
-> main()

(Pdb) n
退出成功

Answer 1

Google search "Power pdb user"

After reading + a little practice, you will be able to master pdb

PS: I think the official documentation about pdb is too short and does not introduce pdb clearly at all