浮点数对象
**********

PyFloatObject

   这个C类型 "PyObject" 的子类型代表一个Python浮点数对象。

PyTypeObject PyFloat_Type

   This instance of "PyTypeObject" represents the Python floating
   point type.  This is the same object as "float" and
   "types.FloatType".

int PyFloat_Check(PyObject *p)

   当他的参数是一个C类型 "PyFloatObject" 或者是C类型 "PyFloatObject"
   的子类型时，返回真。

   在 2.2 版更改: Allowed subtypes to be accepted.

int PyFloat_CheckExact(PyObject *p)

   当他的参数是一个C类型 "PyFloatObject" 但不是C类型 "PyFloatObject"
   的子类型时，返回真。

   2.2 新版功能.

PyObject* PyFloat_FromString(PyObject *str, char **pend)
    *Return value: New reference.*

   Create a "PyFloatObject" object based on the string value in *str*,
   or *NULL* on failure.  The *pend* argument is ignored.  It remains
   only for backward compatibility.

PyObject* PyFloat_FromDouble(double v)
    *Return value: New reference.*

   根据 *v* 创建一个C类型 "PyFloatObject" 对象，失败时返回 *NULL* 。

double PyFloat_AsDouble(PyObject *pyfloat)

   返回一个代表 *pyfloat* 内容的C类型 "double"。如果 *float* 不是一个
   Python浮点数对象，但是包含 "__float__()" 方法，这个方法会首先被调用
   ，将 *pyfloat* 转换成一个浮点数。失败时这个方法返回 "-1.0"，所以应
   该调用C函数 "PyErr_Occurred()" 检查错误。

double PyFloat_AS_DOUBLE(PyObject *pyfloat)

   Return a C "double" representation of the contents of *pyfloat*,
   but without error checking.

PyObject* PyFloat_GetInfo(void)

   Return a structseq instance which contains information about the
   precision, minimum and maximum values of a float. It’s a thin
   wrapper around the header file "float.h".

   2.6 新版功能.

double PyFloat_GetMax()

   Return the maximum representable finite float *DBL_MAX* as C
   "double".

   2.6 新版功能.

double PyFloat_GetMin()

   Return the minimum normalized positive float *DBL_MIN* as C
   "double".

   2.6 新版功能.

int PyFloat_ClearFreeList()

   Clear the float free list. Return the number of items that could
   not be freed.

   2.6 新版功能.

void PyFloat_AsString(char *buf, PyFloatObject *v)

   Convert the argument *v* to a string, using the same rules as
   "str()". The length of *buf* should be at least 100.

   This function is unsafe to call because it writes to a buffer whose
   length it does not know.

   2.7 版后已移除: Use "PyObject_Str()" or "PyOS_double_to_string()"
   instead.

void PyFloat_AsReprString(char *buf, PyFloatObject *v)

   Same as PyFloat_AsString, except uses the same rules as "repr()".
   The length of *buf* should be at least 100.

   This function is unsafe to call because it writes to a buffer whose
   length it does not know.

   2.7 版后已移除: Use "PyObject_Repr()" or "PyOS_double_to_string()"
   instead.
