There are, however, enough ways to crash Python with \code{ctypes}, so
you should be careful anyway.
-Python integers, strings and unicode strings are the only objects that
-can directly be used as parameters in these function calls.
+\code{None}, integers, longs, byte strings and unicode strings are the
+only native Python objects that can directly be used as parameters in
+these function calls. \code{None} is passed as a C \code{NULL} pointer,
+byte strings and unicode strings are passed as pointer to the memory
+block that contains their data (\code{char *} or \code{wchar{\_}t *}). Python
+integers and Python longs are passed as the platforms default C
+\code{int} type, their value is masked to fit into the C type.
Before we move on calling functions with other parameter types, we
have to learn more about \code{ctypes} data types.
\code{char}
}
{
-character
+1-character
+string
+}
+\lineiii{
+\class{c{\_}wchar}
+}
+{
+\code{wchar{\_}t}
+}
+{
+1-character
+unicode string
}
\lineiii{
\class{c{\_}byte}
\code{char}
}
{
-integer
+int/long
}
\lineiii{
\class{c{\_}ubyte}
\code{unsigned char}
}
{
-integer
+int/long
}
\lineiii{
\class{c{\_}short}
\code{short}
}
{
-integer
+int/long
}
\lineiii{
\class{c{\_}ushort}
\code{unsigned short}
}
{
-integer
+int/long
}
\lineiii{
\class{c{\_}int}
\code{int}
}
{
-integer
+int/long
}
\lineiii{
\class{c{\_}uint}
\code{unsigned int}
}
{
-integer
+int/long
}
\lineiii{
\class{c{\_}long}
\code{long}
}
{
-integer
+int/long
}
\lineiii{
\class{c{\_}ulong}
\code{unsigned long}
}
{
-long
+int/long
}
\lineiii{
\class{c{\_}longlong}
\code{long long}
}
{
-long
+int/long
}
\lineiii{
\class{c{\_}ulonglong}
\code{unsigned long long}
}
{
-long
+int/long
}
\lineiii{
\class{c{\_}float}
\code{void *}
}
{
-integer or
-\code{None}
+int/long
+or \code{None}
}
\end{tableiii}
\end{quote}
\subsubsection{Return types\label{ctypes-return-types}}
-By default functions are assumed to return integers. Other return
-types can be specified by setting the \member{restype} attribute of the
-function object.
+By default functions are assumed to return the C \code{int} type. Other
+return types can be specified by setting the \member{restype} attribute of
+the function object.
-Here is a more advanced example, it uses the strchr function, which
+Here is a more advanced example, it uses the \code{strchr} function, which
expects a string pointer and a char, and returns a pointer to a
string:
\begin{verbatim}
\begin{datadescni}{pythonapi}
An instance of \class{PyDLL} that exposes Python C api functions as
-attributes. Note that all these functions are assumed to return
-integers, which is of course not always the truth, so you have to
+attributes. Note that all these functions are assumed to return C
+\code{int}, which is of course not always the truth, so you have to
assign the correct \member{restype} attribute to use these functions.
\end{datadescni}
anything.
It is possible to assign a callable Python object that is not a
-ctypes type, in this case the function is assumed to return an
-integer, and the callable will be called with this integer,
+ctypes type, in this case the function is assumed to return a
+C \code{int}, and the callable will be called with this integer,
allowing to do further processing or error checking. Using this
is deprecated, for more flexible postprocessing or error checking
use a ctypes data type as \member{restype} and assign a callable to the
or error information for a function or method call.
\end{classdesc*}
-\begin{classdesc*}{py_object}
-Represents the C \code{PyObject *} datatype.
-\end{classdesc*}
+\code{py{\_}object} : classdesc*
+\begin{quote}
+
+Represents the C \code{PyObject *} datatype. Calling this with an
+without an argument creates a \code{NULL} \code{PyObject *} pointer.
+\end{quote}
The \code{ctypes.wintypes} module provides quite some other Windows
specific data types, for example \code{HWND}, \code{WPARAM}, or \code{DWORD}.
the second item specifies the type of the field; it can be any
ctypes data type.
-For integer type fields, a third optional item can be given. It
-must be a small positive integer defining the bit width of the
-field.
+For integer type fields like \class{c{\_}int}, a third optional item can
+be given. It must be a small positive integer defining the bit
+width of the field.
Field names must be unique within one structure or union. This is
not checked, only one field can be accessed when names are
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