Why does time.sleep not complain when passed True?

Question

So I just tracked down a strange bug in my Python program which was caused by that fact that I mixed up arguments to a function and mistakenly passed True to time.sleep() . Python seems to silently convert True to 1

The docs say:

Suspend execution for the given number of seconds. The argument may be a floating point number ...

In general, Python is happy to throw exceptions when input does not match the expected type or range. Why does sleep silently convert True to a number?

Answer 1

In python, Bool is a subclass of int

>>> issubclass(bool, int)
True

Here's the source from svn: http://svn.python.org/projects/python/trunk/Modules/timemodule.c

PyArg_ParseTuple converts the arg to a float with the d: specifier

static PyObject *
time_sleep(PyObject *self, PyObject *args)
{
    double secs;
    if (!PyArg_ParseTuple(args, "d:sleep", &secs))
        return NULL;
    if (floatsleep(secs) != 0)
        return NULL;
    Py_INCREF(Py_None);
    return Py_None;
}