boost::python: howto call a function that expects a pointer? -

i have function takes int-pointer , exposed via boost::python. how can call function python?

in c++ boost::python:

void foo(int* i); ... def("foo", foo); 

in python:

import foo_ext = 12 foo_ext.foo(i) 

results in

traceback (most recent call last):   file "<stdin>", line 1, in <module> boost.python.argumenterror: python argument types in foo(int) did not match c++ signature: foo(int* i) 

so how pass pointer?

short answer is: can't. python not have pointers

long answer is: there assorted workarounds depending on use-case.

i notice using int , int* in example. int (along float, str, , bool) special case because immutable in python.

lets object passing in not int.

have wrapper function takes argument reference, takes address , passes on actual function. work seamlessly in python.

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ok, int. have problem. can not change int passed in. if try same solution, boost::python complain l-values @ runtime. there still several options.

let's not need see int looks after function exits , know function not squirrel away pointer dereference after function returns:

your wrapper should take int value or const reference. else same.

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maybe need see after state (the int out perimeter):

your wrapper function take no arguments, , pass address of local int actual function. return value. if function has return value should return tuple.

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both input , output important , know function not squirrel away pointer dereference after function returns:

combine 2 above. wrapper takes 1 int value , returns different int.

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the function expects squirrel away pointer dereference after function returns:

there no real solution. can create , expose object in c++ contains c++ int. wrapper take object reference, extract address of contained int , pass on actual function. keeping object alive in python (and safe garbage collector) until library done python writer's problem, , if goofs data corrupt or interpretor crashes.