在python交互模式下，如何查看类内部变量的值？

Question

When I run a script with python -i file.py and I recieve an error, I would like to find out the value of that variable. However it is inside a class, and not an instance.

class Foo:
    def func(self):
        action_dict = self.socket_resp() # a function that recieves some response from a socket. 
        print(action_dict['bar'])

python -i foo.py

KeyError no 'bar' in action_dict

action_dict

NameError: name 'action_dict' is not defined'

How do I get the value of the action_dict variable in interactive mode

Answer 1

Yes you can get it. The exception from -i will be available in sys.last_value . First import sys and save the sys.last_value to a variable! If you typo, the exception will be lost for good!

Then you can import the traceback module and inspect the activation records, which includes local variables in all call frames!

Thus we get:

% python3 -i file.py
Traceback (most recent call last):
  File "file.py", line 6, in <module>
    Foo().func()
  File "file.py", line 4, in func
    print(action_dict['bar'])
KeyError: 'bar'
>>> import sys
>>> exc = sys.last_value
>>> import traceback
>>> [*traceback.walk_tb(exc.__traceback__)][-1][0].f_locals
{'action_dict': {'foo': 'spam'}, 'self': <__main__.Foo object at 0x7f6aa2e6b978>}