Draw axis lines or the origin for Matplotlib contour plot

Question

I want to draw x=0 and y=0 axis in my contour plot, using a white color. If that is too cumbersome, I would like to have a white dot denoting where the origin is.

My contour plot looks as follows and the code to create it is given below.

xvec = linspace(-5.,5.,100)                               
X,Y = meshgrid(xvec, xvec)                                
fig = plt.figure(figsize=(6, 4))                      
contourf(X, Y, W,100)                             
plt.colorbar()                                    

Answer 1

There are a number of options (E.g. centered spines), but in your case, it's probably simplest to just use axhline and axvline.

E.g.

import numpy as np
import matplotlib.pyplot as plt

xvec = np.linspace(-5.,5.,100)                               
x,y = np.meshgrid(xvec, xvec)
z = -np.hypot(x, y)                                

plt.contourf(x, y, z, 100)                             
plt.colorbar() 

plt.axhline(0, color='white')
plt.axvline(0, color='white')

plt.show()

Answer 2

Can't you just overlay a straight line?

plt.plot([0,0],[-4,4],lw=3,'w')