how to get all the "variables" of a string formating?

[GHUM]

imagine:


template=""" Hello %(name)s, how are you %(action)s"""


we can use it to do things like:

print template % dict (name="Guido", action="indenting")


Is there an easy (i.e.: no regex) way to do get the names of all
parameters?

get_parameters(template) should return ["name", "action"]


Python has to do this somewhere internally..... how to access this
knowledge?

Harald