[Numpy-discussion] Alternative to record array

Jean-Baptiste Rudant boogaloojb@yahoo...
Mon Dec 29 09:58:09 CST 2008


I like to use record arrays to access fields by their name, and because they are esay to use with pytables. But I think it's not very effiicient for what I have to do. Maybe I'm misunderstanding something.

Example : 

import numpy as np
age = np.random.randint(0, 99, 10e6)
weight = np.random.randint(0, 200, 10e6)
data = np.rec.fromarrays((age, weight), names='age, weight')
# the kind of operations I do is :
data.age += data.age + 1
# but it's far less efficient than doing :
age += 1
# because I think the record array stores [(age_0, weight_0) ...(age_n, weight_n)]
# and not [age0 ... age_n] then [weight_0 ... weight_n].

So I think I don't use record arrays for the right purpose. I only need something which would make me esasy to manipulate data by accessing fields by their name.

Am I wrong ? Is their something in numpy for my purpose ? Do I have to implement my own class, with something like :

class FieldArray:
    def __init__(self, array_dict):
        self.array_list = array_dict
    def __getitem__(self, field):
        return self.array_list[field]
    def __setitem__(self, field, value):
        self.array_list[field] = value
my_arrays = {'age': age, 'weight' : weight}
data = FieldArray(my_arrays)

data['age'] += 1

Thank you for the help,

Jean-Baptiste Rudant

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