RenatoL:
> Yes, Jonathan, you're right.
> the question arose precisely from a typo... i had to remove an
> item with key "length"... i wrote "lengt" and the item never went
> away... i knew that "lengt" was not in my key list... This kind of
> mistake is quite tricky, may be using and IDE could help.
This an example that shows that silent failures are sources of bugs...
So this time I don't agree with Jonathan Davis.
Python Zen contains:
Errors should never pass silently.
And Python associative arrays show it:
>>> d = {1:2, 3:4}
>>> del d[5]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyError: 5
The successive rule of the Python Zen says:
Unless explicitly silenced.
Python sets show this at work, they have a 'remove' method that throws if the
item is missing, plus a 'discard' method that acts more like D associative
arrays, in a sense it's a way to silence explicitly the error:
>>> s = set([1, 2])
>>> s.discard(1)
>>> s
set([2])
>>> s = set([1, 2])
>>> s.discard(3)
>>> s
set([1, 2])
>>> s.remove(3)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyError: 3
Maybe D associative arrays too should have both kinds of deleting methods :-)
Bye,
bearophile
