[Numpy-discussion] read not byte aligned records

Gmail aymeric.rateau at gmail.com
Mon May 4 16:17:42 EDT 2015


I am developping a code to read binary files (MDF, Measurement Data File).
In its previous version 3, data was always byte aligned. I used widely
numpy.core.records module (fromstring, fromfile) showing good
performance to read and unpack data on the fly.
However, in the latest version 4, not byte aligned data is possible. It
allows to reduce size of file, especially when raw data is not actually
recorded on bytes, like 10bits for analog converter. For instance, a
record structure could be:
uint64, float32, uint8, unit10, padding 6bits, uint9, padding 7bits,
uint24, uint24, uint24, etc.

I found a way using instead of numpy.core.records the bitstring module
to read these records when not aligned but performance is much worse (I
did not try cython implementation though but in python like x10) ?

Would there be a pure numpy way to do ?



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