How to plot a heatmap of a big matrix with matplotlib (45K * 446)

How to plot a heatmap of a big matrix with matplotlib (45K * 446)

I am trying to plot a heatmap of a big microarray dataset (45K rows per
446 columns). Using pcolor from matplotlib I am unable to do it because my
pc goes easily out of memory (more than 8G)..
I'd prefer to use python/matplotlib instead of R for personal opinion..
Any way to plot heatmaps in an efficient way?
Thanks