Different ways of deleting lists

Question

I want to understand why:

• a = [];
• del a; and
• del a[:];

behave so differently.

I

Answer 1

del a

is removing the variable a from the scope. Quoting from python docs:

Deletion of a name removes the binding of that name from the local or global namespace, depending on whether the name occurs in a global statement in the same code block.

del a[:]

is simply removing the contents of a, since the deletion is passed to the a object, instead of applied to it. Again from the docs:

Deletion of attribute references, subscriptions and slicings is passed to the primary object involved; deletion of a slicing is in general equivalent to assignment of an empty slice of the right type (but even this is determined by the sliced object).

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