Plotting contours for geodetic data.(in Python)

I need to plot contour plot for a geodetic dataset, but I have data for 15 locations of New Zealand. I have been able to generate a map a New Zealand using cartopy library of Python, but I am not sure how to get the contour plot, since the ‘countourf’ function of matplotlib takes in a grid of longitudes and latitudes of the whole concerned area, along with the data at each grid-point. but I only have data for few(15) specific locations.