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Below is a simple building block example of saving data to an hdf5 file while going through eventsThis script lives in /reg/g/psdm/tutorials/examplePython/userSmallHDF5.py.
We do not assume we know the final size of the dataset. The example demonstrates using the hdf5 chunked storage and resize functions to grow a dataset. The same sort of pattern can be used to write in-memory data at the end of a run, but it is easier because at that time the size of the dataset it known.
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import numpy as np
import psana
import h5py
NUM_EVENTS_TO_WRITE=3
ds = psana.DataSource('exp=xpptut15:run=54:smd')
h5out = h5py.File("userSmallData.h5", 'w')
saved = h5out.create_dataset('saved',(0,), dtype='f8', chunks=True, maxshape=(None,))
cspad = psana.Detector('cspad', ds.env())
for idx, evt in enumerate(ds.events()):
if idx > NUM_EVENTS_TO_WRITE: break
calib = cspad.calib(evt)
if (calib is None): continue
saved.resize((idx+1,))
saved[idx] = np.sum(calib)
h5out.close()
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