Another reason assignment expressions would be nice (?)

[alan at littleford.net]

I need to generate some large text files containing test cases for a
project. I decided to exploit the formatted print '%' and the exec()
function. The whole thing is wrapped up with a class (say foo)
instance which supplies useful functions (such as SomeFunction()) so I
can do things like

	a = foo()
	a.setTemplate("'A test line %d' % self.SomeFunction()")
	...
	a.run(100)

Calling run applies exec to the defined templates and so
the idea is the result of this would be hundred lines of: 

	A test line <somenumber>

(Of course the actual example would be more complicated, and class foo
provides loads of useful generator functions). Now here is the rub, I
might want two lines generated with a related value. Lets assume
SomeFunction() throws a random number, so I can't just call it again,
so what I would like to do is this:

	a = foo()
	a.setTemplate("'A test line %d' % 
		(self.i = self.SomeFunction()"))
	a.setTemplate("'Same value as above %d' % self.i")
	...
	a.run(100)

But of course I can't do this because '=' is a statement in the first
template. I could define foo to have some 'assignation' function:

def assign(var, val)
	var[0] = val
	return val

and then use
	
     "'A test line %d' % self.assign(self.var, self.SomeFunction())"
    " 'Same value as above %d' % self.var[0]"

but then the thing gets messy because I have to declare the mutable
array self.var somewhere before using it. All in all it seems I have
to jump through hoops because i = 3 doesn't 'return' the value 3.

Or am I missing something frightfully easy here ..

Tnx
Alan Littleford
alan at littleford.net