Re: pop method question

On Sat, 03 Mar 2007 15:56:39 -0500, Nicholas Parsons wrote:


On Mar 3, 2007, at 3:49 PM, Paul Rubin wrote:

Nicholas Parsons <parsons.nicholas1@xxxxxxxxx> writes:
I was just playing around in IDLE at the interactive prompt and typed
in dir({}) for the fun of it. I was quite surprised to see a pop
method defined there. I mean is that a misnomer or what? From the
literature, pop is supposed to be an operation defined for a stack
data structure. A stack is defined to be an "ordered" list data
structure. Dictionaries in Python have no order but are sequences.
Now, does anyone know why the python core has this pop method
implemented for a dictionary type?

Try typing:

help({}.pop)
--
http://mail.python.org/mailman/listinfo/python-list

Thanks, that gives a more details explanation of what the behavior is
but doesn't answer my question above :(

Just because pop can be defined for an ordered stack doesn't mean pop
can't be generalized to other data types too.

I personally don't see that pop has any advantage, especially since the
most useful example

while some_dict:
do_something_with(some_dict.pop())

doesn't work. Instead you have to write this:

for key in some_dict.keys():
# can't iterate over the dictionary directly!
do_something_with(some_dict.pop(key))

which is hardly any saving over:

for key in some_dict.keys():
# can't iterate over the dictionary directly!
do_something_with(some_dict[key])
del some_dict[key]


To my mind, having to supply a key to dict.pop makes it rather pointless.


--
Steven.

.

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