I want to create a Python wrapper to a C function in a thirdparty library that has a signature such as
int f(double* x);
where the function f
modifies the input argument x
(ie, call by reference using a pointer). What is the most efficient way to implement a Python wrapper function so that the Python user can treat it like a function that just returns a new number each time? Example pseudocode:
# lib and ffi are imported from a compiled cffi.FFI() object
def python_f():
??? double x; ???
rc = lib.f(&x)
assert rc == 0
return x
Should I use the array module (eg, create a "double" array of size 1, pass that to the function, and return the first index)? Is there a more lightweight approach that uses ctypes or cffi helper functions?
def python_f():
x_ptr = ffi.new("double[1]")
x_ptr[0] = old_value
rc = lib.f(x_ptr)
assert rc == 0
return x_ptr[0]
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