Change the values in colorbar to cover all values

I am new to python and Julia. I want add a color bar to a scatter plot. But the values of colorbar just cover one group of points. How can I change the color bar to cover all the values? My code attached.

fig, ax = PyPlot.subplots()
x1 = rand(5:0.1:10, n)
x2 = rand(1:0.1:4, n)

y1 = rand(1:0.1:4, n)
y2 = rand(5:0.1:10, n)

cb1 = rand(6:0.1:10, n)
cb2 = rand(1:0.1:4, n)

sca = ax.scatter(x1, y1, marker="s", c=cb1, s=100)
ax.scatter(x2, y2, marker="o", c=cb2, s=100)

fig.colorbar(sca, ax=ax)