How to Restore an Overwritten Built-in Function in Python?

Restoring an Overwritten Builtin Function

When experimenting in an interactive Python session, it's easy to accidentally overwrite a built-in function like set by assigning it to a variable name. This can be a nuisance, especially if you have a lot of work in progress and don't want to restart your session.

Fortunately, there's a simple way to restore the original set function:

<code class="python">del set</code>

This will remove the masking variable name and grant you access to the original function:

<code class="python">set = 'oops'
set
'oops'
del set
set
<type 'set'></code>

If you still need to access the original set function, you can always do so through the builtins module:

<code class="python">import builtins
builtins.set
<type 'set'></code>

This is useful if you want to override a built-in function but want to retain the ability to call the original function from your override:

<code class="python"># In the Python interpreter
>>> set = lambda x: x
>>> set([1, 2, 2, 3, 4])
[1, 2, 3, 4]
>>> builtins.set([1, 2, 2, 3, 4])
{1, 2, 3, 4}</code>

Remember to check all namespaces for the masking name to avoid confusion. For an overview of scoping rules, see the documentation on Short description of the scoping rules.

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