Is it possible to get string from function?

[Roy Smith]

I realize the subject line is kind of meaningless, so let me explain :-)

I've got some unit tests that look like:

class Foo(TestCase):
  def test_t1(self):
    RECEIPT = "some string"

  def test_t2(self):
    RECEIPT = "some other string"

  def test_t3(self):
    RECEIPT = "yet a third string"

and so on.  It's important that the strings be mutually unique.  In the 
example above, it's trivial to look at them and observe that they're all 
different, but in real life, the strings are about 2500 characters long, 
hex-encoded.  It even turns out that a couple of the strings are 
identical in the first 1000 or so characters, so it's not trivial to do 
by visual inspection.

So, I figured I would write a meta-test, which used introspection to 
find all the methods in the class, extract the strings from them (they 
are all assigned to a variable named RECEIPT), and check to make sure 
they're all different.

Is it possible to do that?  It is straight-forward using the inspect 
module to discover the methods, but I don't see any way to find what 
strings are assigned to a variable with a given name.  Of course, that 
assignment doesn't even happen until the function is executed, so 
perhaps what I want just isn't possible?

It turns out, I solved the problem with more mundane tools:

grep 'RECEIPT = ' test.py | sort | uniq -c

and I could have also solved the problem by putting all the strings in a 
dict and having the functions pull them out of there.  But, I'm still 
interested in exploring if there is any way to do this with 
introspection, as an academic exercise.