Jean-Baptiste Rudant wrote:
Hello,
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
You can accomplish what your FieldArray class does using numpy dtypes: import numpy as np dt = np.dtype([('age', np.int32), ('weight', np.int32)]) N = int(10e6) data = np.empty(N, dtype=dt) data['age'] = np.random.randint(0, 99, 10e6) data['weight'] = np.random.randint(0, 200, 10e6) data['age'] += 1 Timing for recarrays (your code): In [10]: timeit data.age += 1 10 loops, best of 3: 221 ms per loop Timing for my example: In [2]: timeit data['age']+=1 10 loops, best of 3: 150 ms per loop Hope this helps. Ryan -- Ryan May Graduate Research Assistant School of Meteorology University of Oklahoma