I’m new in python, so if the question is unclear or strange, don’t be surprised.
Accidentally made a typo in the console and came across this. Despite the fact that initially variable _ is not defined, if you do any action before try adding 2+_, then _ is defined as a variable and takes the values of the last action.

>>> 2+_
Traceback (most recent call last):   
  File "<stdin>", line 1, in <module>
NameError: name '_' is not defined   
>>> 2+2
4   
>>> 2+_
6   
>>> print(_) 
4   

it doesn’t matter if it’s an arithmetic action or the result of any function. In any case, _ will take any previous value.

>>> print(_) 
4   
>>> type(_) 
<class 'int'>
>>> print(_) 
<class 'int'>
>>>

Variables with a different name can’t do this of course

>>> a  
Traceback (most recent call last):   
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined   
>>> 2+2
4   
>>> 2+a
Traceback (most recent call last):   
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined   
>>>

And only in the python console. This cannot be done in the file. I’m sorry if the question is stupid, it just got interesting for me to understand why _ takes any previous executed value.