CODEWITHSUNDEEP
pythonnumpystructured-array
mgilson
mgilson

Reputation: 309929

numpy fromfile and structured arrays

I'm trying to use numpy.fromfile to read a structured array (file header) by passing in a user defined data-type. For some reason, my structured array elements are coming back as 2-d Arrays instead of flat 1D arrays:

headerfmt='20i,20f,a80'
dt = np.dtype(headerfmt)
header = np.fromfile(fobj,dtype=dt,count=1)
ints,floats,chars = header['f0'][0], header['f1'][0], header['f2'][0]
#                                ^?               ^?               ^?

How do I modify headerfmt so that it will read them as flat 1D arrays?

Upvotes: 4

Views: 2006

Answers (1)

Joe Kington
Joe Kington

Reputation: 284602

If the count will always be 1, just do:

header = np.fromfile(fobj, dtype=dt, count=1)[0]

You'll still be able to index by field name, though the repr of the array won't show the field names.

For example:

import numpy as np

headerfmt='20i,20f,a80'
dt = np.dtype(headerfmt)

# Note the 0-index!
x = np.zeros(1, dtype=dt)[0]

print x['f0'], x['f1'], x['f2']
ints, floats, chars = x

It may or may not be ideal for your purposes, but it's simple, at any rate.

Upvotes: 2

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