#following is pythonification of
#http://root.cern.ch/root/roottalk/roottalk01/2875.html
from ROOT import TColor
#suggest calling with ng = number of grays = 100
def palette(ng):
    cols = []
    for i in range(ng):
        cols.append(TColor(501+i,1-float(i)/ng,1-float(i)/ng,1-float(i)/ng,'')
                    
    
    >   Int_t palette[colNum];
    >   for (Int_t i=0;i<colNum;i++) {
    >      TColor *color = new TColor(501+i
                                      >                                ,1-Float_t(i)/colNum
                                      >                                ,1-Float_t(i)/colNum
                                      >                                ,1-Float_t(i)/colNum,"");
    >      palette[i] = 501+i;
    >   }
    >   gStyle->SetPalette(colNum,palette);
    >
    >   TF2 *f2 = new TF2("f2","exp(-(x^2) - (y^2))",-1.5,1.5,-1.5,1.5);
    >   f2->SetContour(colNum);
    >   f2->Draw("contz");
    >}