Contour plot in Python importing txt table file

Question

I am trying to make a contour plot like:

Using a table of data like 3 columns in a txt file

Answer 1

The code below worked for me:

import scipy.interpolate    
import numpy as np  

N = 500 #number of points for plotting/interpolation    
x, y, z = np.genfromtxt(r'data.dat', unpack=True)
xll = x.min();  xul = x.max();  yll = y.min();  yul = y.max()

xi = np.linspace(xll, xul, N)
yi = np.linspace(yll, yul, N)
zi = scipy.interpolate.griddata((x, y), z, (xi[None,:], yi[:,None]), method='cubic')

contours = plt.contour(xi, yi, zi, 6, colors='black')
plt.clabel(contours, inline=True, fontsize=7)
plt.imshow(zi, extent=[xll, xul, yll, yul], origin='lower', cmap=plt.cm.jet, alpha=0.9)
plt.xlabel(r'$x$')
plt.ylabel(r'$y$')
plt.clim(0, 1)
plt.colorbar()
plt.show()