Lowpass Hann filter in Python
You should read the documentation when using new functions: scipy.signal.firwin


You either provide pass_zero option or two cutoff frequencies. So in your case you don't have to use this option.
The first argument corresponds to the length of the filter. So it has to be an odd integer.
You either provide the sampling frequency or express the cutoff frequencies as relative frequencies (in your case something like fc1/fs).


In summary, for a a filter of order n, you can get your coefficients as

signal.firwin(n + 1, [fc1, fc2], fs=fs, window='hann')