[Tutor] array of different datatypes

[Reed O'Brien]

On Sep 22, 2008, at 11:50 PM, Steve Willoughby wrote:

> Dinesh B Vadhia wrote:
>> Thanks Steve.  How do you sort on the second element of each list  
>> to get:
>> a' = [[42, 'fish'],
>>        [1, 'hello']
>>        [2, 'world']
>>        ]
>
> something like this would do the trick:
>
> a_prime = sorted(a, key=(lambda i: i[1]))
>
> sorted(a) returns a new list consisting of the elements in a
> but in sorted order.  the key= parameter says how to derive the
> sort key from any given element; in this case, the elements
> being sorted are themselves lists, and element #1 in the sub-list
> (a.k.a. "row") is the key.

try itemgetter:

In [1]: a = [[42, 'fish'],
    ...:      [2, 'world'],
    ...:      [1, 'hello']]

In [2]: from operator import itemgetter
In [3]: sorted(a, key=itemgetter(1))

Out[3]: [[42, 'fish'], [1, 'hello'], [2, 'world']]



>
>
>> From: Steve Willoughby Sent: Monday, September 22, 2008 8:16 PM
>> To: Dinesh B Vadhia Cc: tutor at python.org Subject: Re: [Tutor] array  
>> of different datatypes
>> Dinesh B Vadhia wrote:
>>> I have looked (honestly!) and cannot see an array structure to  
>>> allow different datatypes per column.  I need a 2 column array  
>>> with column 1 = an integer and column 2 = chars, and after  
>>> populating the array, sort on column 2 with column 1 sorted  
>>> relatively.
>> If by "array" you mean a regular Python list, the data type of
>> every single element may be different.  So it's just how lists
>> always work.
>> a = [[1, 'hello'],
>>      [2, 'world'],
>>      [42, 'fish'],
>>     ]
>>> Thanks!
>>>
>>> Dinesh
>>>
>>>
>>>
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>>>
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