How do I undo True = False in python interactive mode?
PythonBooleanPython 2.xPython Problem Overview
So I tried the "evil" thing Ned Deily mentioned in his answer here. Now I have that the type True is now always False. How would I reverse this within the interactive window?
Thing to not do:
True = False
Since True has now been completely overridden with False, there doesn't seem to be an obvious way to back-track. Is there a module that True comes from that I can do something like:
True = <'module'>.True
Python Solutions
Solution 1 - Python
You can simply del your custom name to set it back to the default:
>>> True = False
>>> True
False
>>> del True
>>> True
True
>>>
Solution 2 - Python
This works:
>>> True = False
>>> True
False
>>> True = not False
>>> True
True
but fails if False has been fiddled with as well. Therefore this is better:
>>> True = not None
as None cannot be reassigned.
These also evaluate to True regardless of whether True has been reassigned to False, 5, 'foo', None, etc:
>>> True = True == True # fails if True = float('nan')
>>> True = True is True
>>> True = not True or not not True
>>> True = not not True if True else not True
>>> True = not 0
Solution 3 - Python
Another way:
>>> True = 1 == 1
>>> False = 1 == 2
Solution 4 - Python
For completeness: Kevin mentions that you could also fetch the real True from __builtins__:
>>> True = False
>>> True
False
>>> True = __builtins__.True
>>> True
True
But that True can also be overriden:
>>> __builtins__.True = False
>>> __builtins__.True
False
So better to go with one of the other options.
Solution 5 - Python
Just do this:
True = bool(1)
Or, because booleans are essentially integers:
True = 1
Solution 6 - Python
Solutions that use no object literals but are as durable as 1 == 1. Of course, you can define False once True is defined, so I'll supply solutions as half pairs.
def f(): pass
class A(): pass
True = not f()
False = A != A
False = not (lambda:_).__gt__(_)
True = not (lambda:_).__doc__