I am a noob with Cython and C++, so I have a question on argument passing. I want to avoid passing a copy of an argument in the following scenario:
# somefile.pyx
#distutils: language = c++
from libcpp.vector cimport vector
def add_one(vector[int] vect):
cdef int i
n = vect.size()
for i in range(n):
vect[i] += 1
cdef vector[int] v
for i in range(100000):
v.push_back(i)
add_one(v) # <-- ??
I want the method add_one
to just modify v
"in-place." I believe in C++, you can achieve this by pre-pending the argument with &
, which means that any changes to the pointer is passed to the pointee. That way, you don't have to worry about passing a pointer or the actual object, ie
add_one(v); # in c++
Can I do the same in Cython, or do I have to explicitly change the arg type to a reference instead, ie def add_one(vector[int]* vect)
?
Found the answer to my own question. Apparently, you can pass by reference, but the function MUST be cdef
'ed, not def
'ed. ie
# somefile.pyx
#distutils: language = c++
from libcpp.vector cimport vector
cdef void add_one(vector[int]& vect):
cdef int i
n = vect.size()
for i in range(<int>n):
vect[i] += 1
cdef vector[int] v
for i in range(100000):
v.push_back(i)
add_one(v)
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