FFT resolution bandwidth
The bandwidth of each FFT result bin is inversely proportional to the length of the FFT window.  For a wider bandwidth per bin, use a shorter FFT.  If you have more data, then Welch's method can be used with sequential STFT windows to get an average estimate.
I have a numpy fft for a large number of samples. How do I reduce the resolution bandwidth, so that it will show me fewer frequency bins, with averaged power output?