Type feedback tool?

[Martin Vilcans]

Hi list,

I'm wondering if there's a tool that can analyze a Python program
while it runs, and generate a database with the types of arguments and
return values for each function. In a way it is like a profiler, that
instead of measuring how often functions are called and how long time
it takes, it records the type information. So afterwards, when I'm
reading the code, I can go to the database to see what data type
parameter "foo" of function "bar" typically has. It would help a lot
with deciphering old code.

When I googled this, I learned that this is called "type feedback",
and is used (?) to give type information to a compiler to help it
generate fast code. My needs are much more humble. I just want a
faster way to understand undocumented code with bad naming.

--
martin@librador .com

http://www.librador.com

[Scott David Daniels]

Re: Type feedback tool?

Martin Vilcans wrote:

Hi list,
>
I'm wondering if there's a tool that can analyze a Python program
while it runs, and generate a database with the types of arguments and
return values for each function. In a way it is like a profiler, that
instead of measuring how often functions are called and how long time
it takes, it records the type information. So afterwards, when I'm
reading the code, I can go to the database to see what data type
parameter "foo" of function "bar" typically has. It would help a lot
with deciphering old code.
>
When I googled this, I learned that this is called "type feedback",
and is used (?) to give type information to a compiler to help it
generate fast code. My needs are much more humble. I just want a
faster way to understand undocumented code with bad naming.
>

It should be pretty easy to do this as a decorator, then (perhaps
automatically) sprinkle it around your source.

def watch(function) :
def wrapped(*args, **kwargs):
argv = map(type, args)
argd = dict((key, type(value)) for key, value
in kwargs.iteritem s())
try:
result = function(*args, **kwargs)
except Exception, exc:
record_exceptio n(function, type(exc), argv, argd)
raise
else:
record_result(f unction, type(result), argv, argd)
return wrapped

then fill your normal code with:

@watch
def somefun(arg, defarg=1):
...
...


Finally record_* could write to a data structure (using bits like
function.__name __, and f.__module__, and possibly goodies from inspect).
Then you wrap your actual code start with something like:

try:
main(...)
finally:
<write data structure to DB>


--Scott David Daniels
Scott.Daniels@A cm.Org