Hanning in Numpy | Python

The Hanning window is a taper formed by using a weighted cosine.

Syntax:  numpy.hamming(M)

Parameters: 
M :  Number of points in the output window.

Returns:  AN array

The window, with the maximum value normalized to one (the value one appears only if M is odd).

Code #1:

import numpy as np


print(np.hanning(12))

Output:

[ 0.          0.07937323  0.29229249  0.57115742  0.82743037  0.97974649
  0.97974649  0.82743037  0.57115742  0.29229249  0.07937323  0.        ]

Code #2: Plotting the window and its frequency response (requires SciPy and matplotlib).

import numpy as np
import matplotlib.pyplot as plt
from numpy.fft import fft, fftshift

window = np.hanning(51)

plt.plot(window)
plt.title("Hann window")
plt.ylabel("Amplitude"")
plt.xlabel("Sample")

plt.show()

Output:

For frequency:

import numpy as np
import matplotlib.pyplot as plt
from numpy.fft import fft, fftshift

window = np.hanning(51)
plt.figure()

A = fft(window, 2048) / 25.5
mag = np.abs(fftshift(A))
freq = np.linspace(-0.5, 0.5, len(A))
response = 20 * np.log10(mag)
response = np.clip(response, -100, 100)

plt.plot(freq, response)
plt.title("Frequency response of Hanning window")
plt.ylabel("Magnitude [dB]")
plt.xlabel("Normalized frequency [cycles per sample]")
plt.axis("tight")
plt.show()

Output: