[Tutor] dict['_find']

[Max Niederhofer]

Steven, Alan, Knacktus,

thanks for your help. I was indeed very confused because I thought
'_find' was calling something special instead of just being added to
the dictionary (the confusion stemming from
http://www.python.org/dev/peps/pep-0004/ where find module is
obsolete).

When I ran the code, the error I got was:

max:python max$ python ex40.py
State? (ENTER to quit) > CA
Traceback (most recent call last):
  File "ex40.py", line 22, in <module>
    city_found = cities['_find'](cities, state)
  File "ex40.py", line 8, in find_city
    return themap(state)
TypeError: 'dict' object is not callable

Two main mistakes: (1) not including the actual search in the while
loop and (2) wrong parentheses in return themap(state) instead of
return themap[state].

Fixed version which runs:

cities = {'CA': 'San Francisco', 'MI': 'Detroit', 'FL': 'Jacksonville'}

def find_city(themap, state):
	if state in themap:
		return themap[state]
	else:
		return "Not found."

cities['_find'] = find_city

while True:
	print "State? (ENTER to quit)",
	state = raw_input ("> ")	
	if not state: break
	city_found = cities['_find'](cities, state)
	print city_found

Thanks for your help, especially the comments about keeping things
separate and explicit. Now to find out why Zed Shaw thinks this is a
good way of doing it...

Best,
Max

On Sun, Feb 20, 2011 at 9:40 AM, Knacktus <knacktus at googlemail.com> wrote:
> Am 20.02.2011 05:14, schrieb Max Niederhofer:
>
>> Hello all,
>
> Hello Max,
>>
>> first post, please be gentle. I'm having serious trouble finding an
>> alternative for the deprecated find module for dictionaries.
>>
>> The code (from Zed Shaw's Hard Way, exercise 40) goes something like
>> this. Hope indentation survives.
>>
>> cities = {'CA': 'San Francisco', 'MI': 'Detroit', 'FL': 'Jacksonville'}
>
> I use a naming convention for dicts that has made me very happy on several
> occasion ;-):
> key_to_value, in your case
> state_to_city = {...}
>>
>> def find_city(themap, state):
>>     if state in themap:
>>         return themap[state]
>>     else:
>>         return "Not found."
>>
>> cities['_find'] = find_city
>
> Did you put this entry into the same dictionary as the data on purpose?
> Or is the purpose a kind of dispatch? Something that could be a dict on its
> own, like
> private_function_name_to_function = {'_find': find_city}
> You should try to keep things seperate and explicit.
>>
>> while True:
>>     print "State? (ENTER to quit)",
>>     state = raw_input(">  ")
>>
>>     if not state: break
>>
>> city_found = cities['_find'](cities, state)
>> print city_found
>>
>> My question is - how do I rewrite this using an alternate module given
>> find is deprecated? Grateful for all suggestions or pointers. For
>> reference, I'm using 2.6.1 on darwin.
>>
>> Thanks so much for your help.
>>
>> Best,
>> Max
>>
>> --
>> Dr. Maximilian Niederhofer
>> Founder, Qwerly
>> http://qwerly.com/ | http://qwerly.com/max
>> +44 78 3783 8227
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-- 
Dr. Maximilian Niederhofer
Founder, Qwerly
http://qwerly.com/ | http://qwerly.com/max
+44 78 3783 8227