fromitertoolsimportcountfrommathimportcopysign# https://pypi.org/project/prefixed/fromprefixedimportFloatfrommatplotlib.tickerimportScalarFormatterclassFrequencyFormatter(ScalarFormatter):defformat_data(self,value):# Add the Hz suffixreturn'{:H}Hz'.format(Float(value))def_set_order_of_magnitude(self):super()._set_order_of_magnitude()c=abs(self.orderOfMagnitude)# Search 0, -3, 3, -6, 6, -9, 9 etc until the best scientifically# prefixed oom is found, and then set self.orderOfMagnitude to itforsciOomincount(3,3):ifc<sciOom:self.orderOfMagnitude=copysign(sciOom,self.orderOfMagnitude)break# fig,ax...ax.yaxis.set_major_formatter(FrequencyFormatter(# I'm not necessarily interested in this, but without this,# ScalarFormatter.get_offset doesn't use my own .format_data function to# format also the offset.useMathText=True))