Re: [python-win32] How Can I exec() a statement?

[Gabriel Genellina]

At Thursday 7/4/2005 10:53, * William wrote:

Please stay in the list - and even move to the Python-list as those topics are not specific to Windows.

Exactly what I want to do -- for the enquiry about "what" I want to do, it is best to use as an example.

#4

b = 2

print "Before:"

print "   a = %s" % str( a )

print "   b = %s" % str( b )#

codeLine = 'a = b + 6'

exec codeLine  in globals(), locals()

#

print "After:"

print "   a = %s"% str( a )

print "   b = %s" % str( b )

... of course the notion, is a little more elaborate though still in its infancy.  I am thinking it will be a basic verification tool or even an aid for debugging.  By chopping up the line, I can print the value of all the symbols in the codeLine.  The 'trick' is going to be Not calling functions twice (in case there is a side-effect). 

So you are going to write your own debugger? I'd try the existing ones first :)

It's hard to recognize automatically the relevant symbols, even using the tokenize/token/parser modules.
Unles you restrict yourself to very simple expressions with no objects, no attribute selection, no subscripting...
         a[round(math.sin(2*math.pi*obj.current_angle/180.0+obj.phase))]*x+config['offset']
There is a lot of names there: a,round,math,sin,pi,obj... Some just make sense in the context of another (by example, there is no phase variable, it's an attribute of obj). Maybe current_angle is a property and getting its value actually means invoking a function wich reads a sensor...

 For example, I'd like a way to get the symbol name for variable a above.  Is there a function like "nameOF( a )"?

Maybe a Python hacker guru could say something, but AFAIK, once you get inside the function nameOF( a ), there is no way to tell where its argument came from. In the following example, I think there is no way to distinguish inside f if it was called with a or b as an argument, since both are simply names pointing to the same object:

>>> def f(x):
...   print x, id(x)
...
>>>
>>> a = [1,2,3]
>>> b = a
>>> a
[1, 2, 3]
>>> b
[1, 2, 3]
>>> id(a)
6999440
>>> id(b)
6999440
>>> f(a)
[1, 2, 3] 6999440
>>> f(b)
[1, 2, 3] 6999440
>>>

Gabriel Genellina
Softlab SRL

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