import matplotlib.pyplot as mpl
import cartopy.crs as ccrs

fig = plt.figure()
ax = fig.add_subplot(projection=ccrs.PlateCarree())
ax.coastlines()
gl = ax.gridlines(draw_labels=True,
                  xlocs=np.arange(-180,181,30), ylocs=np.arange(-90,91,30),
                  linewidth=0.5, color='silver',
                  xlabel_style={'rotation':270})
gl.top_labels = False
gl.left_labels = False