numpy-union-example.py

#!/usr/bin/env python3
import os
import numpy as np

mydtype = np.dtype({
	'names': 'x y xy'.split(),
	'formats': 'f4 f4 2f4'.split(),
	'offsets': [0, 4, 0]
})

mapfile = "numpy-union-example.dat"
if os.path.exists(mapfile):
	os.unlink(mapfile)

mapped = np.memmap(
	mapfile,
	shape=(1,),
	dtype=mydtype,
	mode='w+')

mapped[0]['xy'] = np.nan

record = np.empty((), dtype=mydtype)
record['xy'] = np.nan

mapped[0] = record # THIS is where it crashes