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OpenVMS
Python
Modules
cython
Commits
e7209d64ef2c
Commit
e7209d64ef2c
authored
9 years ago
by
Robert Bradshaw
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Update C++ Rectangle example.
parent
9bb933bd3aff
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robertwb-rect
robertwb-rect_bookmark
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docs/src/userguide/wrapping_CPlusPlus.rst
+48
-29
48 additions, 29 deletions
docs/src/userguide/wrapping_CPlusPlus.rst
with
48 additions
and
29 deletions
docs/src/userguide/wrapping_CPlusPlus.rst
+
48
−
29
View file @
e7209d64
...
@@ -48,5 +48,6 @@
...
@@ -48,5 +48,6 @@
class Rectangle {
class Rectangle {
public:
public:
int x0, y0, x1, y1;
int x0, y0, x1, y1;
Rectangle();
Rectangle(int x0, int y0, int x1, int y1);
Rectangle(int x0, int y0, int x1, int y1);
~Rectangle();
~Rectangle();
...
@@ -51,5 +52,3 @@
...
@@ -51,5 +52,3 @@
Rectangle(int x0, int y0, int x1, int y1);
Rectangle(int x0, int y0, int x1, int y1);
~Rectangle();
~Rectangle();
int getLength();
int getHeight();
int getArea();
int getArea();
...
@@ -55,4 +54,5 @@
...
@@ -55,4 +54,5 @@
int getArea();
int getArea();
void getSize(int* width, int* height)
void move(int dx, int dy);
void move(int dx, int dy);
};
};
}
}
...
@@ -65,6 +65,8 @@
...
@@ -65,6 +65,8 @@
namespace shapes {
namespace shapes {
Rectangle::Rectangle() { }
Rectangle::Rectangle(int X0, int Y0, int X1, int Y1) {
Rectangle::Rectangle(int X0, int Y0, int X1, int Y1) {
x0 = X0;
x0 = X0;
y0 = Y0;
y0 = Y0;
...
@@ -74,7 +76,7 @@
...
@@ -74,7 +76,7 @@
Rectangle::~Rectangle() { }
Rectangle::~Rectangle() { }
int Rectangle::get
Length
() {
int Rectangle::get
Area
() {
return (x1 - x0);
return (x1 - x0)
* (y1 - y0)
;
}
}
...
@@ -79,11 +81,8 @@
...
@@ -79,11 +81,8 @@
}
}
int Rectangle::getHeight() {
void Rectangle::getSize(int *width, int *height) {
return (y1 - y0);
width = x1 - x0;
}
height = y1 - y0;
int Rectangle::getArea() {
return (x1 - x0) * (y1 - y0);
}
}
void Rectangle::move(int dx, int dy) {
void Rectangle::move(int dx, int dy) {
...
@@ -192,5 +191,6 @@
...
@@ -192,5 +191,6 @@
cdef extern from "Rectangle.h" namespace "shapes":
cdef extern from "Rectangle.h" namespace "shapes":
cdef cppclass Rectangle:
cdef cppclass Rectangle:
Rectangle() except +
Rectangle(int, int, int, int) except +
Rectangle(int, int, int, int) except +
int x0, y0, x1, y1
int x0, y0, x1, y1
...
@@ -195,5 +195,3 @@
...
@@ -195,5 +195,3 @@
Rectangle(int, int, int, int) except +
Rectangle(int, int, int, int) except +
int x0, y0, x1, y1
int x0, y0, x1, y1
int getLength()
int getHeight()
int getArea()
int getArea()
...
@@ -199,4 +197,5 @@
...
@@ -199,4 +197,5 @@
int getArea()
int getArea()
void getSize(int* width, int* height)
void move(int, int)
void move(int, int)
Note that the constructor is declared as "except +". If the C++ code or
Note that the constructor is declared as "except +". If the C++ code or
...
@@ -229,7 +228,7 @@
...
@@ -229,7 +228,7 @@
...
...
Note that, like C++, if the class has only one constructor and it
Note that, like C++, if the class has only one constructor and it
is a
default
one, it's not necessary to declare it.
is a
nullary
one, it's not necessary to declare it.
Create Cython wrapper class
Create Cython wrapper class
----------------------------
----------------------------
...
@@ -239,7 +238,7 @@
...
@@ -239,7 +238,7 @@
external Python code (which is our whole point).
external Python code (which is our whole point).
Common programming practice is to create a Cython extension type which
Common programming practice is to create a Cython extension type which
holds a C++ instance
pointer
as an attribute
``thisptr``,
and create a bunch of
holds a C++ instance as an attribute and create a bunch of
forwarding methods. So we can implement the Python extension type as::
forwarding methods. So we can implement the Python extension type as::
cdef class PyRectangle:
cdef class PyRectangle:
...
@@ -243,5 +242,5 @@
...
@@ -243,5 +242,5 @@
forwarding methods. So we can implement the Python extension type as::
forwarding methods. So we can implement the Python extension type as::
cdef class PyRectangle:
cdef class PyRectangle:
cdef Rectangle
*thisptr
# hold a C++ instance which we're wrapping
cdef Rectangle
c_rect
# hold a C++ instance which we're wrapping
def __cinit__(self, int x0, int y0, int x1, int y1):
def __cinit__(self, int x0, int y0, int x1, int y1):
...
@@ -247,11 +246,9 @@
...
@@ -247,11 +246,9 @@
def __cinit__(self, int x0, int y0, int x1, int y1):
def __cinit__(self, int x0, int y0, int x1, int y1):
self.thisptr = new Rectangle(x0, y0, x1, y1)
self.c_rect = Rectangle(x0, y0, x1, y1)
def __dealloc__(self):
def get_area(self):
del self.thisptr
return self.c_rect.getArea()
def getLength(self):
def get_size(self)
return self.thisptr.getLength()
int width, int height
def getHeight(self):
self.c_rect.getSize(&width, &height)
return self.thisptr.getHeight()
return width, height
def getArea(self):
return self.thisptr.getArea()
def move(self, dx, dy):
def move(self, dx, dy):
...
@@ -257,4 +254,4 @@
...
@@ -257,4 +254,4 @@
def move(self, dx, dy):
def move(self, dx, dy):
self.
thisptr
.move(dx, dy)
self.
c_rect
.move(dx, dy)
And there we have it. From a Python perspective, this extension type will look
And there we have it. From a Python perspective, this extension type will look
...
@@ -259,5 +256,8 @@
...
@@ -259,5 +256,8 @@
And there we have it. From a Python perspective, this extension type will look
And there we have it. From a Python perspective, this extension type will look
and feel just like a natively defined Rectangle class. If you want to give
and feel just like a natively defined Rectangle class.
It should be noted that
If you want to give
attribute access, you could just implement some properties::
attribute access, you could just implement some properties::
...
@@ -262,8 +262,27 @@
...
@@ -262,8 +262,27 @@
attribute access, you could just implement some properties::
attribute access, you could just implement some properties::
property x0:
@property
def __get__(self): return self.thisptr.x0
def x0(self):
def __set__(self, x0): self.thisptr.x0 = x0
return self.c_rect.x0
@x0.setter
def x0(self):
def __set__(self, x0): self.c_rect.x0 = x0
...
Cython initializes C++ class attributes of a cdef class using the nullary constructor.
If the class you're wrapping does not have a nullary constructor, you must store a pointer
to the wrapped class and manually allocate and deallocate it.
A convienient and safe place to do so is in the `__cinit__` and `__dealloc__` methods
which are guaranteed to be called exactly once upon creation and deletion of the Python
instance.
cdef class PyRectangle:
cdef Rectangle* c_rect # hold a pointer to the C++ instance which we're wrapping
def __cinit__(self, int x0, int y0, int x1, int y1):
self.c_rect = new Rectangle(x0, y0, x1, y1)
def __dealloc__(self):
del self.c_rect
...
...
If you prefer giving the same name to the wrapper as the C++ class, see the
If you prefer giving the same name to the wrapper as the C++ class, see the
...
...
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