python对象str的find和index区别

﹏ヽ暗。殇╰゛Y 2022-05-19 02:36 162阅读 0赞

代码可以直接看github上的一个干净代码：https://github.com/wklken/Python-2.7.8

python内置的类型在解释器中实现，相关的内置类型见：https://docs.python.org/2/library/stdtypes.html

对应实现的类是：[Objects][]/**stringobject.c**

**index方法**

PyDoc_STRVAR(index__doc__,
    "S.index(sub [,start [,end]]) -> int\n\
    \n\
    Like S.find() but raise ValueError when the substring is not found.");
    
    static PyObject *
    string_index(PyStringObject *self, PyObject *args)
    {
        Py_ssize_t result = string_find_internal(self, args, +1);
        if (result == -2)
            return NULL;
        if (result == -1) {
            PyErr_SetString(PyExc_ValueError,
                            "substring not found");
            return NULL;
        }
        return PyInt_FromSsize_t(result);
    }

find方法

PyDoc_STRVAR(rfind__doc__,
    "S.rfind(sub [,start [,end]]) -> int\n\
    \n\
    Return the highest index in S where substring sub is found,\n\
    such that sub is contained within S[start:end].  Optional\n\
    arguments start and end are interpreted as in slice notation.\n\
    \n\
    Return -1 on failure.");
    
    static PyObject *
    string_rfind(PyStringObject *self, PyObject *args)
    {
        Py_ssize_t result = string_find_internal(self, args, -1);
        if (result == -2)
            return NULL;
        return PyInt_FromSsize_t(result);
    }

总结：实际上内部内什么区别，就是在没有找到对应字符串，是一个异常，还是返回-1

**参考资料：**

[https://docs.python.org/2.0/api/][https_docs.python.org_2.0_api]   Python/C API Reference Manual

[Objects]: https://github.com/wklken/Python-2.7.8/tree/master/Objects
[https_docs.python.org_2.0_api]: https://docs.python.org/2.0/api/