Finding the variables (read or write)

Chris Angelico rosuav at
Mon Jan 14 22:28:28 CET 2013

On Tue, Jan 15, 2013 at 6:48 AM,  <servekarimi at> wrote:
> I'd like to develop a small debugging tool for python programs.In Dynamic Slicing How can I find the variables that are accessed in a statement? And find the type of access (read or write) for those variables (in Python).
> ### Write: A statement can change the program state.
> ### Read : A statement can read the program state .
> **For example in these 4 lines we have:
> (1) x = a+b    => write{x} & read{a,b}
> (2) y=6        => write{y} & read{}
> (3) while(n>1) => write{} & read{n}
> (4) n=n-1      => write{n} & read{n}

An interesting question. What's your definition of "variable"? For
instance, what is written and what is read by this statement:

self.lst[2] += 4

Is "self.lst" considered a variable? (In C++ etc, this would be a
member function manipulating an instance variable.) Or is "self" the
variable? And in either case, was it written to? What about:


(which might collect Fibonacci numbers)?


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