how can I clear a dictionary in python

[Larry Bates]

Bruno Desthuilliers wrote:
> Larry Bates a écrit :
>> Aahz wrote:
>>> In article <4_SdndYI-pFUbZfbnZ2dnUVZ_hzinZ2d at comcast.com>,
>>> Larry Bates  <lbates at websafe.com> wrote:
>>>> Marko.Cain.23 at gmail.com wrote:
>>>>> I create a dictionary like this
>>>>> myDict = {}
>>>>>
>>>>> and I add entry like this:
>>>>> myDict['a'] = 1
>>>>> but how can I empty the whole dictionary?
>>>> just point myDict to an empty dictionary again
>>>>
>>>> myDict={}
>>> Go back and read Christian's post, then post a followup explaning why
>>> his
>>> solution is better than yours.  Your explanation should use id().
>>
>> I believe he (as many new to Python do) are mired in old
>> programming thinking that variables "contain" things.
> 
> Does "he" refer to Christian Tismer ? If so, you may want to use google
> and correct your beliefs (hint: does 'stackless Python' ring a bell ?).
> 
>> As I'm sure you kno, variables point to things in Python.
> 
> (conceptually) names are keys associated with an object in a given
> namespace. FWIW, be assured that Christians knows this pretty well.
> 
>> I don't believe that there are lots of other objects
>> pointing to this dictionary.
> 
> You just cannot *know* this. This might be true now, this might be false
> now, and this might change anytime. Assuming anything here is the road
> to disaster. Don't assume, do the righ thing.
> 
>>  Perhaps the OP can clarify
>> for us.  If there aren't other objects pointing to
>> this dictionary it would make NO sense to iterate over a
>> dictionary and delete all the keys/values
> 
> You don't iterate over anything. Dicts being the central datastructure
> in Python, you can bet your ass they are optimized to death (or near
> death). If you have any doubt, then still don't assume : verify (hint:
> import timeit). And yet even if clearing a dict happens to be a bit
> slower than instanciating a new one, rebinding a name and mutating an
> object are still two very different concepts in Python, with very
> different consequences. The OP explicitely asked for clearing a dict,
> not for creating a new one.
> 
>> so I tried to read
>> between the lines
> 
> Why ?
> 
>> and answer what I believe the OP thought he
>> was asking.
> 
> What the OP asked was quite clear, and not subject to any
> interpretation. And the correct answer is obviously not the one you gave.
> 
>>  BTW-I didn't see you posting an answer to what
>> you thought was the "correct" question, just criticizing me
>> for taking the time to answer what I perceived the OP was
>> asking.
> 
> If you cannot understand the difference between criticism and a friendly
> correction,  nor why you should actually thank the one correcting you
> when you're wrong, I guess there's no point trying explaining why
> correcting wrong answers on newsgroups is actually important.

I stand corrected about my answer, but I'll stick to my assumption
(until told otherwise by the OP) that the question that was asked
wasn't precisely what the OP wanted to accomplish.  It was just too
simple to mean what you guys assumed (e.g. complex dictionary pointed
to by lots of other objects, etc.).  I don't mind being corrected with
the proper information, but Aahz's post doesn't make any sense.  He said
"Go back and read Christian's answer...". Christian's answers were not
answers to the OP's question at all.  Here is what shows up in my
newsreader:

'''
Reading the Python docs might help.
But before, I would try a dir(myDict).
Maybe you will find an easter-egg
which has exactly the name you are looking for?

cheers - chris
'''

and

'''
This is wrong and not answering the question.
Creating a new dict does not change the dict.
He wants to clear *this* dict, and maybe he
cannot know how many other objects are
referring to this dict.

cheers -- chris
'''

You appear to be the only one that apparently posted the correct
answer myDict.clear() for which I thank you.  I learned two things
today: 1) answer EXACTLY the question that is asked and 2) dicts
have a clear method that is safer than my answer.

-Larry