Create a matplotlib figure with a colorbar using gridspec.

cbar_subplot.py

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec
from numpy.random import randint

# Generate array of random values
data = randint(0, 
               high=100, 
               size=(100, 100))

# GridSpec object. second column will hold colorbar
# you can play with the ratio of widths to get the look you want
# Can also play with the spacing between subplos using wspace kwarg
gs = GridSpec(nrows=1,
              ncols=2,
              width_ratios=(100, 5),
              wspace=.005)

# figure object
fig = plt.figure()

# Add an ax object to draw imshow on.
ax = fig.add_subplot(gs[0])

# save imge output so we can supply it when calling colorbar
im = ax.imshow(data)

# Can use position kwarg to modify position and size of cbar.
cbarax = fig.add_subplot(gs[1]),

cbar = plt.colorbar(im, 
                    orientation='vertical', 
                    cax=cbarax)

plt.show()