Interpolation using matplotlib tricontourf function in python

Question

I'm fairly new to python programming. The data I'm working with is generated by filtering process via a third party software, such that there are three arrays, x, y and z that don't need to be arranged in a 2d grid and its contour plot can be derived using tricontourf(x,y,z) or tricontour(z,y,z) function from matplotlib library.

However, the contour plot appears as shown below . For some perspective, here is the last 50 rows of the data in three arrays (x, y and z):

33.000000   -6.000000   -0.5318
34.000000   -6.000000   -0.851
35.000000   -6.000000   -1.2272
36.000000   -6.000000   -1.5542
37.000000   -6.000000   -1.7379
38.000000   -6.000000   -1.7604
39.000000   -6.000000   -1.6388
40.000000   -6.000000   -1.4163
41.000000   -6.000000   -1.1581
42.000000   -6.000000   -0.9236
21.000000   -7.000000   -0.1708
22.000000   -7.000000   -0.071
23.000000   -7.000000   -0.1835
24.000000   -7.000000   -0.4963
25.000000   -7.000000   -0.905
26.000000   -7.000000   -1.2861
27.000000   -7.000000   -1.517
28.000000   -7.000000   -1.5054
29.000000   -7.000000   -1.2797
30.000000   -7.000000   -0.9375
31.000000   -7.000000   -0.5956
32.000000   -7.000000   -0.3749
33.000000   -7.000000   -0.3736
34.000000   -7.000000   -0.5786
35.000000   -7.000000   -0.9207
36.000000   -7.000000   -1.3124
37.000000   -7.000000   -1.6598
38.000000   -7.000000   -1.8716
39.000000   -7.000000   -1.9304
24.000000   -8.000000   -0.2939
25.000000   -8.000000   -0.702
26.000000   -8.000000   -1.1314
27.000000   -8.000000   -1.4689
28.000000   -8.000000   -1.6089
29.000000   -8.000000   -1.5114
30.000000   -8.000000   -1.2546
31.000000   -8.000000   -0.9426
32.000000   -8.000000   -0.6808
33.000000   -8.000000   -0.5766
34.000000   -8.000000   -0.6864
35.000000   -8.000000   -0.9568
36.000000   -8.000000   -1.3126
27.000000   -9.000000   -1.2369
28.000000   -9.000000   -1.4891
29.000000   -9.000000   -1.5975
30.000000   -9.000000   -1.5301
31.000000   -9.000000   -1.3623
32.000000   -9.000000   -1.1902
33.000000   -9.000000   -1.0836
30.000000   -10.000000  -1.8646

The data is stored in such a way that it triangularly projects downwards in the 2d frame. I'd like to know how to extrapolate the contours to completely fill the rectangular frame as shown below . It is derived via surfer software using the same data set. Any help shall be highly appreciated. Preferably, kriging interpolation may be adopted.