TypeError: Cannot cast array data from dtype('S4') to dtype('float64') according to the rule 'safe'

[trungdtbk]

I use basemap-1.1.0. I got this exception. I figure out it is probably because of these methods in PrintoMap():
self.wmap.drawcoastlines(linewidth = '0.75')
self.wmap.drawcountries(linewidth = '0.75')

When I remove the quote marks, it works.