h5cat: quickly preview HDF5 file contents from the command-line

As a first attempt at writing actually useful blog posts, I’ll publicise a small Python script I wrote to peek inside HDF5 files when HDFView is overkill. Sometimes you just want to know how many dimensions a stored array has, or its exact path within the HDF hierarchy.

The “codebase” is currently tiny enough that it all fits below:

#!/usr/bin/env python

import os, sys, argparse
import h5py
from numpy import array

arguments = argparse.ArgumentParser(add_help=False)
arggroup = arguments.add_argument_group('HDF5 cat options')
arggroup.add_argument('-g', '--group', metavar='GROUP',
    help='Preview only path given by GROUP')
arggroup.add_argument('-v', '--verbose', action='store_true', default=False,
    help='Include array printout.')

if __name__ == '__main__':
    parser = argparse.ArgumentParser(
        description='Preview the contents of an HDF5 file',
    parser.add_argument('fin', nargs='+', help='The input HDF5 files.')

    args = parser.parse_args()
    for fin in args.fin:
        print '>>>', fin
        f = h5py.File(fin, 'r')
        if args.group is not None:
            groups = [args.group]
            groups = []
        for g in groups:
            print '\n   ', g
            if type(f[g]) == h5py.highlevel.Dataset:
                a = f[g]
                print '      shape: ', a.shape, '\n      type: ', a.dtype
                if args.verbose:
                    a = array(f[g])
                    print a

h5cat is available on GitHub under an MIT license. Here’s an example use case:

$ h5cat -v -g vi single-channel-tr3-0-0.00.lzf.h5
>>> single-channel-tr3-0-0.00.lzf.h5

      shape:  (3, 1) 
      type:  float64
[[ 0.        ]
 [ 0.06224902]
 [ 2.23062383]]

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