[Tutor] Grouping based on attributes of elements in a List

[Eli Nazarova]

On 3/29/2011 4:03 PM, ranjan das wrote:
> I have the following list
>
> List=[( 'G1', 'CFS', 'FCL', 'R1' ),('G3', 'LOOSEFREIGHT', 'MIXEDLCL', 
> 'R9'), ('G4', 'CFS', 'FCL', 'R10' ), ('G2',  'LOOSEFREIGHT', 'LCL', 
> 'R4' ), ('G1', 'CFS', 'FCL', 'R2' ), ('G2', 'LOOSEFREIGHT', 'LCL', 
> 'R5')  ]
>
>
> now I want to group this elements of List  first by index [1] that is 
> (CFS and LOOSEFREIGHT ) together and for those elements which are 
> grouped together for LOOSEFREIGHT, i want to further divide them into 
> different groups based on index[2] that is (LCL or MIXEDLCL)
>
>
> So essentially i want them grouped into different lists and my 
> solution should be  of the form
>
> New_List=[ [ ( 'G1', 'CFS', 'FCL', 'R1' ), ('G1', 'CFS', 'FCL', 'R2' 
> ), ('G4', 'CFS', 'FCL', 'R10' ) ], [ ('G2',  'LOOSEFREIGHT', 'LCL', 
> 'R4' ), ('G2', 'LOOSEFREIGHT', 'LCL', 'R5' )], [ ('G3', 
> 'LOOSEFREIGHT', 'MIXEDLCL', 'R9')] ]
>
> How do I do it?
>
> I managed to do divide them into different lists based on index [1] 
> however I was not able to further divide them  based on index [2]
>
> Any help is appreciated
>
>
>
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You can you list comprehension (three times) checking for membership of 
the relevant items, or you can use for loop to go over all available 
tuples and sort them into different lists using if. In any case, after 
that you create a list of the three required lists.

Eli
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