NameError: name 'plt' is not defined

# Draw digit image
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)

# Major ticks every 20, minor ticks every 5
major_ticks = np.arange(0, 29, 5)
minor_ticks = np.arange(0, 29, 1)

ax.set_xticks(major_ticks)
ax.set_xticks(minor_ticks, minor=True)
ax.set_yticks(major_ticks)
ax.set_yticks(minor_ticks, minor=True)

# And a corresponding grid
ax.grid(which='both')

# Or if you want different settings for the grids:
ax.grid(which='minor', alpha=0.2)
ax.grid(which='major', alpha=0.5)

ax.imshow(x_test[selected_digit], cmap=plt.cm.binary)

plt.show()

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-24-1e41385f9397> in <module>
      1 # Draw digit image
----> 2 fig = plt.figure()
      3 ax = fig.add_subplot(1, 1, 1)
      4 
      5 # Major ticks every 20, minor ticks every 5