How to make custom hatching range in matplotlib?

Question

The Issue

I have two 100x100 arrays- one with data (which I'll call array1) and one with some smaller, scaled data (which I'll call array2). I created a test array to see where array2 + array1 is above or below certain thresholds, and the results for each point should be one of three results- array1 + array2 for that point is >5, >10, or neither (<5). Depending on the result, I created a new 100x100 array (array3) and assigned a 1., 2., or 0. to that point, respectively.

Now I want to plot array1 & array3 using plt.contourf(), and I want the latter subplot to have hatching. I want the range of that hatching to be x=0, x=1, and x=2. Looking at the documentation I know I probably can't do it that way, so instead I'll say x<1, 1<=x,<2, and x=>2. Only problem is I don't know how to specify those ranges.

The code (working example)

Here's the full code of the problem.

#Make data array1
array1 = np.empty([10,10])
for i in range(10):
    for j in range(10):
        array1[i,j] = i+j
print array1

#Make data array2
array2 = np.empty([10,10])
for i in range(10):
    for j in range(10):
        array2[i,j] = (i*0.25)+(j*0.25)
print array2

#Make range test array3
array3 = np.empty([10,10])
for i in range(10):
    for j in range(10):
        if array1[i,j]+array2[i,j] > 5 and array1[i,j]+array2[i,j] > 10:
            array3[i,j] = 2
        elif array1[i,j]+array2[i,j] > 5:
            array3[i,j] = 1
        else:
            array3[i,j] = 0
print array3

#Plot
from matplotlib.patches import Ellipse, Polygon
xgrid = np.arange(0,10)
ygrid = np.arange(0,10)
n_levels=2
plt.contourf(xgrid, ygrid, array1)
stip = plt.contourf(xgrid, ygrid, array3, n_levels, colors='none',
              hatches=[None,'.', '/'],
              extend='lower')
#create a legend for the contour set
artists, labels = stip.legend_elements()
plt.legend(artists, labels, handleheight=2)
plt.show

Note the legend. I want the ranges to be x<1, 1<=x,<2, and x=>2, not what the package automatically assigns.

The Question

How can I assign custom ranges to my hatching? I plan to get this example working so I can translate it to a Basemap plot where I have lat-lon data, and on top of that a stippled array of where that lat-lon data is compared to the data+S.D. of two other arrays. I wanted various stippling depending on, for each grid point, if that lat-lon data is > one data+S.D. array, the other data+S.D. array, or both arrays.

Answer 1

For more control on the contour levels use the levels keyword.

stip = plt.contourf(xgrid, ygrid, array3, levels=[-1, 0, 1, 2],
                    colors='none', hatches=[None,'.', '/'])
artists, labels = stip.legend_elements()
plt.legend(artists, labels, handleheight=2)