Another interesting parameter for a lot of functions is transform (unlike orientation or pivot this parameter can also be used in e.g. plot).
The transform parameter allows you to add a transformation, specified by a Transform object. For the sake of example, this is how you would rotate the plot of some random data:
import numpy
from matplotlib import pyplot, transforms
data = numpy.random.randn(100)
# first of all, the base transformation of the data points is needed
base = pyplot.gca().transData
rot = transforms.Affine2D().rotate_deg(90)
# define transformed line
line = pyplot.plot(data, 'r--', transform= rot + base)
# or alternatively, use:
# line.set_transform(rot + base)
pyplot.show()
For an example on how to rotate a patch, see this answer, which was also the source of inspiration for this answer.
update
I recently found out that the transform parameter does not work as expected when using pyplot.scatter (and other PathCollections). In this case, you might want to use the offset_transform. See this answer for more information on how to the offset_transform can be set.