This program creates a VLArray using PyTables. One dimensional Numpy arrays of varying length are appended as rows.

vlarrayExample.py

##################################################################################
#						                                 #																	
# This program creates a VLArray using PyTables. One dimensional numpy arrays of #
# varying length are appended as rows			                         #					#						                                 #	
#						                                 #																	 																				 				
###################################################################################

import tables as tb
import numpy as np

#initialize
filename='vlarrayEx.h5'
atom=tb.Int32Atom(shape=())

#open hdf5 file and create an vlarray
fileh=tb.openFile(filename,'w')
vlarray=fileh.createVLArray(fileh.root,'vlarray',atom,"Experimental VL Array", \
											filters=tb.Filters(1))

#append variable length rows
vlarray.append(np.array([x for x in range(10)]))
vlarray.append(np.array([x**2 for x in range(2)]))
vlarray.append(np.array([x**3 for x in range(3)]))

#close file
fileh.close()

#open the file again to append
file1=tb.openFile(filename,'a')
root=file1.root
print "root --> ", root
arr=root.vlarray
#print file1

#append more rows
arr.append(np.array([4*x for x in range(4)]))

#read the strings in the file
for s in arr:
	print '%s [%d] --> %s' % (arr.name,arr.nrow,s)
	
#close the file
file1.close()