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Accessing AST at runtime

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  Accessing AST at runtime alessandromoura35@googlemail.com - 2012-09-01 19:30 -0700
    Re: Accessing AST at runtime Ramchandra Apte <maniandram01@gmail.com> - 2012-09-01 19:48 -0700
    Re: Accessing AST at runtime Terry Reedy <tjreedy@udel.edu> - 2012-09-02 02:05 -0400

#28229 — Accessing AST at runtime

Hi,

I would like to access the AST of a python object at runtime. I mean, if I have this:

def f(x): return x*x/2

Is there any way to interrogate the object f to find out the AST of the expression x*x/2 ? Of course if the definition of f were in a file, I could use the ast module to parse it; but what I want is to do this from within the code.

The closest thing I was able to find was f.__code__, and more specifically f.__code__.co_code, but that is a byte-string which seems to be the bytecode (?) for the function.

This may not be possible at all; maybe after the def statement is processed by the Python interpreter the AST information is discarded. But I wanted to check here if someone knows one way or another.

Many thanks.

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#28230

On Sunday, 2 September 2012 08:00:59 UTC+5:30, (unknown)  wrote:
> Hi,
> 
> 
> 
> I would like to access the AST of a python object at runtime. I mean, if I have this:
> 
> 
> 
> def f(x): return x*x/2
> 
> 
> 
> Is there any way to interrogate the object f to find out the AST of the expression x*x/2 ? Of course if the definition of f were in a file, I could use the ast module to parse it; but what I want is to do this from within the code.
> 
> 
> 
> The closest thing I was able to find was f.__code__, and more specifically f.__code__.co_code, but that is a byte-string which seems to be the bytecode (?) for the function.
> 
> 
> 
> This may not be possible at all; maybe after the def statement is processed by the Python interpreter the AST information is discarded. But I wanted to check here if someone knows one way or another.
> 
> 
> 
> Many thanks.

You could scan the text for code and then ast.parse() it.
Then you know how...

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#28237

On 9/1/2012 10:30 PM, alessandromoura35@googlemail.com wrote:
> Hi,
>
> I would like to access the AST of a python object at runtime. I mean,
> if I have this:
>
> def f(x): return x*x/2
>
> Is there any way to interrogate the object f to find out the AST of
> the expression x*x/2 ? Of course if the definition of f were in a
> file, I could use the ast module to parse it; but what I want is to
> do this from within the code.
>
> The closest thing I was able to find was f.__code__, and more
> specifically f.__code__.co_code, but that is a byte-string which
> seems to be the bytecode (?) for the function.
>
> This may not be possible at all; maybe after the def statement is
> processed by the Python interpreter the AST information is discarded.

Yes, it is.

-- 
Terry Jan Reedy

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