[英]Clean Way to Convert Python 3 Unicode to std::string
I wrap a lot of C++ using the Python 2 API (I can't use things like swig or boost.python for various technical reasons).我使用 Python 2 API 包装了很多 C++(由于各种技术原因,我不能使用 swig 或 boost.python 之类的东西)。 When I have to pass a string (usually a path, always ASCII) into C/C++, I use something like this:
当我必须将一个字符串(通常是一个路径,总是 ASCII)传递到 C/C++ 中时,我使用这样的东西:
std::string file_name = PyString_AsString(py_file_name);
if (PyErr_Occurred()) return NULL;
Now I'm considering updating to Python 3, where PyString_*
methods don't exist.现在我正在考虑更新到 Python 3,其中
PyString_*
方法不存在。 I found one solution that says I should do something like this:我找到了一个解决方案,说我应该做这样的事情:
PyObject* bytes = PyUnicode_AsUTF8String(py_file_name);
std::string file_name = PyBytes_AsString(bytes);
if (PyErr_Occurred()) return NULL;
Py_DECREF(bytes);
However this is twice as many lines and seems a bit ugly (not to mention that it could introduce a memory leak if I forget the last line).然而,这是行数的两倍,看起来有点难看(更不用说如果我忘记了最后一行,它可能会导致内存泄漏)。
The other option is to redefine the python functions to operate on bytes
objects, and to call them like this另一种选择是重新定义 python 函数来操作
bytes
对象,并像这样调用它们
def some_function(path_name):
_some_function(path_name.encode('utf8'))
This isn't terrible, but it does require a python-side wrapper for each function.这并不可怕,但它确实需要每个函数的 python 端包装器。
Is there some cleaner way to deal with this?有没有更干净的方法来处理这个问题?
Looks like the solution exists in python 3.3, with char* PyUnicode_AsUTF8(PyObject* unicode)
.看起来解决方案存在于 python 3.3 中,带有
char* PyUnicode_AsUTF8(PyObject* unicode)
。 This should be exactly the same behavior as the PyString_AsString()
function from python 2.这应该与 Python 2 中的
PyString_AsString()
函数完全相同。
If you know (and of course, you could check with an assert or similar) that it's all ASCII, then you could simply create it like this:如果你知道(当然,你可以用断言或类似的东西来检查)它都是 ASCII,那么你可以简单地像这样创建它:
std::string py_string_to_std_string(PyUnicode_string py_file_name)
{
len = length of py_file_name; // Not sure how you write that in python.
std::string str(len);
for(int i = 0; i < len; i++)
str += py_file_name[i];
return str;
}
Providing an improved version of accepted answer , instead of using PyUnicode_AsUTF8(...)
better to use PyUnicode_AsUTF8AndSize(...) .提供已接受答案的改进版本,而不是使用
PyUnicode_AsUTF8(...)
更好地使用PyUnicode_AsUTF8AndSize(...) 。
Becasue string may contain null character (0 codepoint) somewhere in the middle, then your resulting std::string
will contain truncated version of full string if you use PyUnicode_AsUTF8(...)
.因为字符串可能在中间的某处包含空字符(0 代码点),那么如果您使用
PyUnicode_AsUTF8(...)
,则生成的std::string
将包含完整字符串的截断版本。
Py_ssize_t size = 0;
char const * pc = PyUnicode_AsUTF8AndSize(obj, &size);
std::string s;
if (pc)
s = std::string(pc, size);
else
// Error, handle!
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