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Some simple tools for managing numpy.recarray objects

Project description


Some simple tools for managing numpy.recarray objects


Install via pip:

pip3 install --user RecarrayTools

Or this repo:

#clone the repo
git clone
cd RecarrayTools

#either use a wheel
python3 bdist_wheel
pip3 install --user dist/RecarrayTools-0.0.3-py3-none-any.whl

#or just install directly
python3 install


This module contains a small number of routines...


This will save a record array to a binary file - note that the dtype of the record array shouldn't be too exotic (object arrays would not work - use pickle for those).

import numpy as np
import RecarrayTools as RT

#create some recarray
dtype = [('a','int32'),('b','float64',(6,))]
arr = np.recarray(10,dtype=dtype)

#fill it
arr.a = blah #shape (10,)
arr.b = stuff #shape (10,6)

#save it

The file format used here is simple:

The first 4 bytes correspond to a 32-bit integer containing the size of the recarray (i.e. arr.size).

Then each field arr.dtype.names is stored contiguously as whatever dtype it was assigned with, one field at a time.

The file created in the above example would be formatted in the following way:

Bytes 0-3 : 32-bit integer - total length of the recarray

Bytes 4-43 : Array of 32-bit integers, length 10 (arr.a)

Bytes 44-523: Array of 64-bit floating points, shape (10,6), length 60



This will read in the files created by SaveRecarray(), e.g.

dtype = [('a','int32'),('b','float64',(6,))]
fname = 'path/to/'
arr = RT.ReadRecarray(fname,dtype)


This reduces the number of fields in a recarray object, e.g.:

#initial object with fields 'a', 'b', 'c' and 'd'
dtype = [('a','int32'),('b','float64',(6,)),('c','int64'),('d','float64')]
obj0 = np.recarray(10,dtype=dtype)

#new object with just fields 'a' and 'c'
obj1 = RT.ReduceRecarray(obj0,['a','c'])


Append two recarrays with identical dtypes:

C = RT.JoinRecarray(A,B)


Append some extra fields to a recarray:

#some initial recarray
A = np.recarray(n,dtype=dtype)

#new fields for the array
x = np.arange(n)
y = x**2

#add them
B = RT.AppendFields(A,[('x','float32'),('y','float32')],(x,y))
#B now has fields B.x and B.y


Interpolate fields within a recarray:

#a would be the initial recarray, b would be the new recarray
#RefField = name of field to interpolate over
#InterpFields = list of names of fields to interpolate
b = RT.InterpRecarrayFields(a,b,RefField='x',InterpFields=['a','b','c','d','x'])

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