import numpy as np
import matplotlib.pyplot as plt

from matplotlib.colors import from_levels_and_colors

cmap, norm = from_levels_and_colors([2, 5, 7, 10], ['red', 'blue', 'green'])
data = np.arange(12).reshape(3, 4)

plt.pcolormesh(data, cmap=cmap, norm=norm)
plt.colorbar()
plt.show()

import numpy as np
import matplotlib.pyplot as plt

from matplotlib.colors import from_levels_and_colors

cmap, norm = from_levels_and_colors([2, 5, 7], ['red', 'blue', 'green'], extend='max')
data = np.arange(12).reshape(3, 4)

plt.pcolormesh(data, cmap=cmap, norm=norm)
plt.colorbar()
plt.show()

import iris.palette
import matplotlib.pyplot as plt
import numpy as np
from matplotlib.colors import NoNorm

nice_cmap = plt.get_cmap('brewer_RdYlBu_11')

plt.figure(figsize=(20, 0.5))
plt.title('The "brewer_RdYlBu_11" cmap')
plt.pcolormesh(np.arange(nice_cmap.N).reshape(1, -1), norm=NoNorm(), cmap=nice_cmap)
ax = plt.gca()
ax.yaxis.set_visible(False)
ax.autoscale_view(tight=True)
plt.show()

import iris
import iris.palette
import iris.quickplot as qplt
from matplotlib.colors import from_levels_and_colors
import matplotlib.pyplot as plt
import numpy as np

fname = iris.sample_data_path('air_temp.pp')
temperature = iris.load_cube(fname)

nice_cmap = plt.get_cmap('brewer_RdYlBu_11')
# Pick some of the nicer colors from the palette...
colors = nice_cmap([9, 8, 6, 3, 2, 0])
levels = [250, 265, 275, 285, 300]

cmap, norm = from_levels_and_colors(levels, colors, extend='both')

plt.figure(figsize=(16, 10))
qplt.pcolormesh(temperature, cmap=cmap, norm=norm)
plt.gca().coastlines()
plt.show()

nice_cmap.peek()