根本原因是getrandbits调用的函数是用C编写的，在GitHub Python repository的源代码中可以查看。
你会发现，getrandbits在底层调用了os模块中的urandom函数，如果你查看这个函数的实现，你会发现它确实是用C语言编写的。
os_urandom_impl(PyObject *module, Py_ssize_t size)
{
PyObject *bytes;
int result;
if (size < 0)
return PyErr_Format(PyExc_ValueError,
"negative argument not allowed");
bytes = PyBytes_FromStringAndSize(NULL, size);
if (bytes == NULL)
return NULL;
result = _PyOS_URandom(PyBytes_AS_STRING(bytes), PyBytes_GET_SIZE(bytes));
if (result == -1) {
Py_DECREF(bytes);
return NULL;
}
return bytes;
}
谈到
randint，如果您查看此函数的源代码，它调用
randrange，后者进一步调用
_randbelow_with_get_randbits。
def randrange(self, start, stop=None, step=_ONE):
"""Choose a random item from range(start, stop[, step]).
This fixes the problem with randint() which includes the
endpoint; in Python this is usually not what you want.
"""
try:
istart = _index(start)
except TypeError:
istart = int(start)
if istart != start:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer arg 1 for randrange()")
_warn('non-integer arguments to randrange() have been deprecated '
'since Python 3.10 and will be removed in a subsequent '
'version',
DeprecationWarning, 2)
if stop is None:
if step is not _ONE:
raise TypeError('Missing a non-None stop argument')
if istart > 0:
return self._randbelow(istart)
raise ValueError("empty range for randrange()")
try:
istop = _index(stop)
except TypeError:
istop = int(stop)
if istop != stop:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer stop for randrange()")
_warn('non-integer arguments to randrange() have been deprecated '
'since Python 3.10 and will be removed in a subsequent '
'version',
DeprecationWarning, 2)
width = istop - istart
try:
istep = _index(step)
except TypeError:
istep = int(step)
if istep != step:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer step for randrange()")
_warn('non-integer arguments to randrange() have been deprecated '
'since Python 3.10 and will be removed in a subsequent '
'version',
DeprecationWarning, 2)
if istep == 1:
if width > 0:
return istart + self._randbelow(width)
raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))
if istep > 0:
n = (width + istep - 1) // istep
elif istep < 0:
n = (width + istep + 1) // istep
else:
raise ValueError("zero step for randrange()")
if n <= 0:
raise ValueError("empty range for randrange()")
return istart + istep * self._randbelow(n)
def randint(self, a, b):
"""Return random integer in range [a, b], including both end points.
"""
return self.randrange(a, b+1)
正如您所见，
randrange函数中的
Try/
Except块涉及许多操作，由于这些额外开销和控制流程，它在Python中运行速度较慢。请注意，保留了HTML标记。
