Matplotlib contour no data coordinates

[b4rtt]

I have problem with Matplotlib contour graph. I have graph size (100x100). All "importance" values of CSV which are >0 should be red. Every value <0 should be blue.

My question is, if is possible to have places with no data (no coordinates in CSV) in white color. Now it's couting some average color from nearby points.

This is situation which I have right now:


This is data visualized by points:


This type of graph that I need:


Is possible to get similar graph by using Contour?

This is my code:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.mlab as ml
import pandas as pd

csv_filename = 'data.csv'
df = pd.read_csv(csv_filename)

data = [df.x_pos, df.y_pos]
x = df.x_pos
y = df.y_pos
z = df.importance


ny, nx = 1000, 1000
xmin, xmax = 0, 100
ymin, ymax = 0, 100

xi = np.linspace(xmin, xmax, nx)
yi = np.linspace(ymin, ymax, ny)


zi = ml.griddata(x, y, z, xi, yi, interp='linear')

plt.contour(xi, yi, zi, 1, linewidths = 0, colors = 'k')
plt.pcolormesh(xi, yi, zi, vmin=-1, vmax=1, cmap = plt.get_cmap('bwr'))

#plt.scatter(x, y, marker = 'o', c = z, s = 10, vmin=-1, vmax=1, cmap = plt.get_cmap('bwr'))
plt.colorbar() 

plt.xlim(xmin, xmax)
plt.ylim(ymin, ymax)
plt.show()

This is CSV data example:

x_pos,y_pos,importance
32,-48,0.87487145766094
32,52,0.43743572883047
32,68,1.127350663193

Full CSV data is here: https://pastebin.com/mYS6LSyG

[b4rtt]

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