Get the length of a Python object. This is equivalent to calling
the Python builtin
len() function on the object.
py_len(x, default = NULL)
The length of the object, as a numeric value.
A Python object.
The default length value to return, in the case that
the associated Python object has no
__len__ method. When
(the default), an error is emitted instead.
Not all Python objects have a defined length. For objects without a defined
py_len() will throw an error. If you'd like to instead
infer a default length in such cases, you can set the
1L, to treat Python objects without a
__len__ method as having