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Building and accessing an array of dictionaries

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  Building and accessing an array of dictionaries Sam <lightaiyee@gmail.com> - 2014-01-16 01:41 -0800
    Re: Building and accessing an array of dictionaries Chris Angelico <rosuav@gmail.com> - 2014-01-16 20:48 +1100
    Re: Building and accessing an array of dictionaries Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-01-16 11:52 +0200
    Re: Building and accessing an array of dictionaries Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-01-16 17:01 +0000
      Re: Building and accessing an array of dictionaries Grant Edwards <invalid@invalid.invalid> - 2014-01-17 20:53 +0000

#64067 — Building and accessing an array of dictionaries

I would like to build an array of dictionaries. Most of the dictionary example on the net are for single dictionary.

dict = {'a':'a','b':'b','c':'c'}
dict2 = {'a':'a','b':'b','c':'c'}
dict3 = {'a':'a','b':'b','c':'c'}

arr = (dict,dict2,dict3)

What is the syntax to access the value of dict3->'a'?

Thank you.

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#64068

On Thu, Jan 16, 2014 at 8:41 PM, Sam <lightaiyee@gmail.com> wrote:
> I would like to build an array of dictionaries. Most of the dictionary example on the net are for single dictionary.
>
> dict = {'a':'a','b':'b','c':'c'}
> dict2 = {'a':'a','b':'b','c':'c'}
> dict3 = {'a':'a','b':'b','c':'c'}
>
> arr = (dict,dict2,dict3)
>
> What is the syntax to access the value of dict3->'a'?

Technically, that's a tuple of dictionaries, and you may want to use a
list instead:

lst = [dict, dict2, dict3]

Like any other list or tuple, you can reference them by their indices:

lst[2] is dict3

lst[2]['a'] is dict3['a']

Hope that helps!

ChrisA

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#64069

Sam writes:

> I would like to build an array of dictionaries. Most of the
> dictionary example on the net are for single dictionary.
> 
> dict = {'a':'a','b':'b','c':'c'}
> dict2 = {'a':'a','b':'b','c':'c'}
> dict3 = {'a':'a','b':'b','c':'c'}
> 
> arr = (dict,dict2,dict3)
> 
> What is the syntax to access the value of dict3->'a'?

This isn't a special case.

arr[2] to get the dictionary
arr[2]['a'] to get the value in the dictionary

'a' in arr[2] to find if there is such a key

arr[2].get('a') to get the value or None if the key isn't there
arr[2].get('a', 'd') to get a value even if the key isn't there

help(dict.get)

for key in arr[2]:
   # to iterate over the keys

The exact same mechanisms are used no matter where you get the
dictionary from.

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#64092

On 16/01/2014 09:48, Chris Angelico wrote:
> On Thu, Jan 16, 2014 at 8:41 PM, Sam <lightaiyee@gmail.com> wrote:
>> I would like to build an array of dictionaries. Most of the dictionary example on the net are for single dictionary.
>>
>> dict = {'a':'a','b':'b','c':'c'}
>> dict2 = {'a':'a','b':'b','c':'c'}
>> dict3 = {'a':'a','b':'b','c':'c'}
>>
>> arr = (dict,dict2,dict3)
>>
>> What is the syntax to access the value of dict3->'a'?
>
> Technically, that's a tuple of dictionaries

For the benefit of lurkers, newbies or whatever it's the commas that 
make the tuple, not the brackets.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence

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#64193

On 2014-01-16, Mark Lawrence <breamoreboy@yahoo.co.uk> wrote:
> On 16/01/2014 09:48, Chris Angelico wrote:
>> On Thu, Jan 16, 2014 at 8:41 PM, Sam <lightaiyee@gmail.com> wrote:
>>> I would like to build an array of dictionaries. Most of the dictionary example on the net are for single dictionary.
>>>
>>> dict = {'a':'a','b':'b','c':'c'}
>>> dict2 = {'a':'a','b':'b','c':'c'}
>>> dict3 = {'a':'a','b':'b','c':'c'}
>>>
>>> arr = (dict,dict2,dict3)
>>>
>>> What is the syntax to access the value of dict3->'a'?
>>
>> Technically, that's a tuple of dictionaries
>
> For the benefit of lurkers, newbies or whatever it's the commas that 
> make the tuple, not the brackets.  

In _that_ example, yes.  There are other cases where it's the
brackets (sort of):

    foo('a','b','c')    # three separate string objects are passed

    foo(('a','b','c'))  # a single tuple object is passed    

-- 
Grant Edwards               grant.b.edwards        Yow! Being a BALD HERO
                                  at               is almost as FESTIVE as a
                              gmail.com            TATTOOED KNOCKWURST.

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