wfdict['samprate'] = int(1.0 / header['delta'])
'int' rounds the sampling rate to the lowest integer but I think it should round to the largest as sometimes header['delta'] is not exact for example: for 20 Hz instead of displaying 0.05 it displays 0.05000001 that makes the sampling rate 19.9999 Hz instead of 20 and the final sampling rate is 19 instead of 20.
I fixed that with:
wfdict['samprate'] = int(numpy.round(1.0 / header['delta']))