When is del useful in python?


Question

I can't really think of any reason why python needs the del keyword (and most languages seem to not have a similar keyword). For instance, rather than deleting a variable, one could just assign None to it. And when deleting from a dictionary, a del method could be added.

Is there any reason to keep del in python, or is it a vestige of Python's pre-garbage collection days?

1
337
5/24/2018 1:24:49 AM

Accepted Answer

Firstly, you can del other things besides local variables

del list_item[4]
del dictionary["alpha"]

Both of which should be clearly useful. Secondly, using del on a local variable makes the intent clearer. Compare:

del foo

to

foo = None

I know in the case of del foo that the intent is to remove the variable from scope. It's not clear that foo = None is doing that. If somebody just assigned foo = None I might think it was dead code. But I instantly know what somebody who codes del foo was trying to do.

454
1/5/2018 5:49:24 AM

There's this part of what del does (from the Python Language Reference):

Deletion of a name removes the binding of that name from the local or global namespace

Assigning None to a name does not remove the binding of the name from the namespace.

(I suppose there could be some debate about whether removing a name binding is actually useful, but that's another question.)


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