How to restore a builtin that I overwrote by accident?

Question

I accidentally overwrote set by using it as a variable name in an interactive python session - is there any way that I can get access to the original set<

Answer 1

Just delete the name that is masking the builtin:

>>> set = 'oops'
>>> set
'oops'
>>> del set
>>> set

You can always still access the original built-in through the builtins module (__builtin__ on Python 2, with underscores and no s); use this if you want to override the built-in but want to defer to the original still from the override:

>>> import builtins
>>> builtins.set

If you have trouble locating where the masking name is defined, do check all namespaces from your current one up to the built-ins; see Short description of the scoping rules? for what scopes may apply to your current situation.