Matplotlib: How to remove white lines in the heatmap

Question

I'm plotting multiple heatmaps. The code is as follows:

import seaborn as sns
import numpy as np
import matplotlib.pyplot as plt
FONTSIZE=20
fig, axes = plt.subplots(nrows=1, ncols=4,figsize=(12,3))
k=0
for ax in axes.flat:
    mat = np.zeros((10,10)) + 0.5
    im = ax.imshow(mat,interpolation='nearest', vmin=0.0, vmax=1.0,cmap='Reds')
    ax.set_xlim([-0.5, 9.0 + 0.5])
    ax.set_ylim([-0.5, 9.0 + 0.5])
    ax.set_xticks([0,5])
    ax.set_yticks([0,5])
    ax.set_xlabel('X',fontsize=FONTSIZE)
    if k == 0:
        ax.set_ylabel('Y',fontsize=FONTSIZE)
    ax.set_title('Title')
    k += 1
# Make an axis for the colorbar on the right side
cax = fig.add_axes([0.99, 0.235, 0.03, 0.682])
cbar = fig.colorbar(im, cax=cax,ticks=[0.0,0.1,0.2,0.3,0.4])
cbar.ax.set_yticklabels(['0.0','0.1','0.2','0.3','0.4'])
figtype = 'jpg'
fig.tight_layout()
fig.savefig('aaa.' + copy(figtype),format = figtype,bbox_inches='tight')

The figure is as follows:

How can I remove the white lines in each subplot? It is astonishing. I find that if I remove the import seaborn as sns, then the white lines disappear. But in that case, the figure will looks ugly.

How can I remove the white lines and in the meanwhile keep the looking of the figure similar to the current looking?

Thank you all for helping me!

Answer 1

You can turn the grid off via

import matplotlib.pyplot as plt
plt.rcParams["axes.grid"] = False

This should be done before importing seaborn.
In seaborn version < 0.8 the import of seaborn automatically sets the style to the darkgrid, which defines axes.grid : True. This would need to be reverted as shown above.