Search the list of objects

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August 16th, 2012, 09:35 AM

4izhik

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Search the list of objects

Hello,

A python newbie here. I have a list of objects each carrying a number of different pieces of data (each object has a a couple of strings, and a whole bunch of parameter values stored in it). I am looking for an efficient way to search through this list of objects to find all the members with a given value for a certain parameter of interest. Basically, I would like to go through the list, call a function that returns the value of the parameter of interest stored inside, and then evaluate if that value is what I am looking for.

So far, I have been creating another 'index' list by, first, looping through my list of objects and adding the values of the parameter of interest for each object to the 'index' list. Then using something like

if x in indexlist: ind = indexlist.index(x)

But, I am hoping there is another way to search my list directly without generating another list.

Thanks a lot and sorry to be so verbose

August 16th, 2012, 11:33 AM

b49P23TIvg

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Alternatives are filter which is builtin or from itertools, or you can use list comprehension. Illustrated list comprehension:

Code:

import re
import pprint

class c:

    def __init__(self,**kwargs):
        self._kwargs = kwargs

    def __getattr__(self,attr):
        try:
            return self._kwargs[attr]
        except KeyError:
            raise AttributeError(attr)

    def __str__(self):
        return pprint.pformat(self._kwargs)

LIST = [c(a=1,b=2,c='behold'),c(b=28,a=2,c='the'),c(a={1,2,3},b=8,c='sea')]

print('objects where b is less than 10:')
print('\n'.join(str(o) for o in LIST if o.b < 10))

print("\nobjects for which attribute c contains 'h'")
search = re.compile('h').search
print('\n'.join(str(o) for o in LIST if search(o.c)))

print('\nobjects where type of a is set:')
print('\n'.join(str(o) for o in LIST if type(o.a) == type(set())))

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Last edited by b49P23TIvg : August 16th, 2012 at 11:35 AM. Reason: Correction: change index error to key error.

August 16th, 2012, 12:25 PM