Graphical user interfaces for Python programs Phần 6 ppsx

FORMAT STRINGS 321 Because of the great variability of each architecture’s C++ compilers, I am not going to try to provide a cookbook to solve the various problems. However, I am going to present some code fragments that have worked for Solaris. To get a module to compile with C++, you need to define the Python API as a C segment to the C++ compiler: extern "C" { #include "Python.h" } Then, the init function must be given the same treatment: extern "C" { DL_EXPORT(void) initstatistics() { Py_InitModule("statistics", statistics_methods); } } 14.5 Format strings Format strings provide a mechanism to specify the conversion of Python types passed as argu- ments to the extension routines. The items in the string must match, in number and type, the addresses supplied in the PyArg_ParseTuple() call. Although the type of the arguments is checked with the format string, the supplied addresses are not checked. Consequently, errors here can have a disastrous effect on your application. Since Python supports long integers of arbitrary length, it is possible that the values can- not be stored in C long integers; in all cases where the receiving field is too small to store the value, the most significant bits are silently truncated. The characters |, :, and ; have special meaning in format strings. "|" This indicates that the remaining arguments in the Python argument list are optional. The C variables corresponding to optional arguments must be initialized to their default value since PyArg_ParseTuple leaves the variables corresponding to absent arguments unchanged. ":" The list of format units ends here; the string after the colon is used as the function name in error messages. ";" The list of format units ends here; the string after the colon is used as the error message instead of the default error message. . that have worked for Solaris. To get a module to compile with C++, you need to define the Python API as a C segment to the C++ compiler: extern "C" { #include " ;Python. h" } Then,. { DL_EXPORT(void) initstatistics() { Py_InitModule("statistics", statistics_methods); } } 14.5 Format strings Format strings provide a mechanism to specify the conversion of Python types passed as argu- ments to the extension routines arguments is checked with the format string, the supplied addresses are not checked. Consequently, errors here can have a disastrous effect on your application. Since Python supports long integers