I just discovered a logical bug in my code which was causing all sorts of problems. I was inadvertently doing a bitwise AND instead of a logical AND.
I changed the code from:
r = mlab.csv2rec(datafile, delimiter=",", names=COL_HEADERS)
mask = ((r["dt"] >= startdate) & (r["dt"] <= enddate))
selected = r[mask]
TO:
r = mlab.csv2rec(datafile, delimiter=",", names=COL_HEADERS)
mask = ((r["dt"] >= startdate) and (r["dt"] <= enddate))
selected = r[mask]
To my surprise, I got the rather cryptic error message:
ValueError: The truth value of an array with more than one element is
ambiguous. Use a.any() or a.all()
Why was a similar error not emitted when I use a bitwise operation – and how do I fix this?