FWHM = round(2 * np.sqrt(2 * np.log(2)) * popt[10], 4)
plt.axvspan(popt[9] - FWHM / 2, popt[9] + FWHM / 2, facecolor='g', alpha=
    0.3, label='FWHM = %s' % FWHM)
plt.legend(fontsize=10)
plt.show()
Gaussian Fit on noisy and 'interesting' data set