x = np.arange(-20., 21.)/5.
np.sinc(x)
# array([ -3.89804309e-17,  -4.92362781e-02,  -8.40918587e-02,
# -8.90384387e-02,  -5.84680802e-02,   3.89804309e-17,
# 6.68206631e-02,   1.16434881e-01,   1.26137788e-01,
# 8.50444803e-02,  -3.89804309e-17,  -1.03943254e-01,
# -1.89206682e-01,  -2.16236208e-01,  -1.55914881e-01,
# 3.89804309e-17,   2.33872321e-01,   5.04551152e-01,
# 7.56826729e-01,   9.35489284e-01,   1.00000000e+00,
# 9.35489284e-01,   7.56826729e-01,   5.04551152e-01,
# 2.33872321e-01,   3.89804309e-17,  -1.55914881e-01,
# -2.16236208e-01,  -1.89206682e-01,  -1.03943254e-01,
# -3.89804309e-17,   8.50444803e-02,   1.26137788e-01,
# 1.16434881e-01,   6.68206631e-02,   3.89804309e-17,
# -5.84680802e-02,  -8.90384387e-02,  -8.40918587e-02,
# -4.92362781e-02,  -3.89804309e-17])

import matplotlib.pyplot as plt
plt.plot(x, np.sinc(x))
# [<matplotlib.lines.Line2D object at 0x...>]
plt.title("Sinc Function")
# <matplotlib.text.Text object at 0x...>
plt.ylabel("Amplitude")
# <matplotlib.text.Text object at 0x...>
plt.xlabel("X")
# <matplotlib.text.Text object at 0x...>
plt.show()

# It works in 2-D as well:

x = np.arange(-200., 201.)/50.
xx = np.outer(x, x)
plt.imshow(np.sinc(xx))
# <matplotlib.image.AxesImage object at 0x...>