PyEval_EvalCodeEx return value

Mark Hammond skippy.hammond at
Fri Sep 23 01:47:12 CEST 2011

On 20/09/2011 8:34 PM, Mateusz Loskot wrote:
> Hi,
> I'm trying to dig out details about what exactly is the return
> value the of PyEval_EvalCodeEx function in Python 3.x
> The documentation is sparse, unfortunately.
> Perhaps I'm looking at wrong function.
> My aim is simple, I need to execute Python code using Python interpreter
> embedded in my C++ application.
> The Python code is a simple script that always returns single value.
> For example:
> #! /usr/bin/env python
> def foo(a, b):
> return a + b
> f = foo(2, 3)
> But, f can be of different type for different script: one returns
> numeric value, another returns a sequence, so the type is not
> possible to be determined in advance.
> I know how to capture Python stdout/stderr.
> I also know how to access the "f" attribute using
> PyObject_GetAttrString and then I can convert "f" value to C++ type
> depending on PyObject type.
> However, I guess there shall be a way to access "f" value
> directly from PyEval_EvalCode return object:
> PyObject* evalRet = ::PyEval_EvalCode(...);
> But, I can't find any details what the "evalRet" actually is.

Eval is to eval an expression.  If you simply eval the expression "f" in 
the context of the module you should get the result returned.  Obviously 
though it is designed to eval more complex expressions and in your 
specific example, doing the getattr thing will also work fine.


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