Possible to get transfer function coefficients from window?
What you are describing is an FIR filter, such that all the denominator coefficients are zero, save the basis, a[0]=1.  So you could do something like:
data_smoothed = scipy.signal.filtfilt(window, 1, data_noisy)

There is a notable point.  The DC gain of the filter is equal to the sum of the coefficients for FIR filters.  Your window is likely normalized to 1, so the sum is probably higher than 1, which means your filter will have gain at low frequencies.  You would want to divide all the coefficients by the sum of the window to keep the gain to unity.