4.2 Calling and data translation errors

Errors may occur when converting Prolog terms to Python objects as defined in section 2. These errors are reported as instantiation_error, type_error(Type, Culprit) or domain_error(Domain, Culprit).

Defined domains are:

py_constant

In a term @(Constant), Constant is not true, false or none. For example, py_call(print(@error)).

py_keyword_arg

In a call to Python, a non keyword argument follows a keyword argument. For example, py_call(m:f(1,x=2,3), R)

py_string_as

The value for a py_string_as(As) option is invalid. For example, py_call(m:f(), R, [py_string_as(codes)])

py_dict_as

The value for a py_dict_as(As) option is invalid. For example, py_call(m:f(), R, [py_dict_as(list)])

py_term

A term being translated to Python is unsupported. For example, py_call(m:f(point(1,2), R).

Defined types are:

py_object

A Python object reference was expected. For example, py_free(42)

rational

A Python fraction instance is converted to a Prolog rational number, but the textual conversion does not produce a valid rational number. This can happen if the Python fraction is subclassed and the __str__() method does not produce a correct string.

py_key_value

Inside a {k:v, ...} representation for a dictionary we find a term that is not a key-value pair. For example, py_call(m:f({a:1, x}), R)

py_set

Inside a py_set(Elements), Elements is not a list. For example, py_call(m:f(py_set(42), R).

py_target

In py_call(Target:FuncOrAttrOrMethod), Target is not a module (atom) or Python object reference. For example, py_call(7:f(), R).

py_callable

In py_call(Target:FuncOrAttrOrMethod), FuncOrAttrOrMethod is not an atom or compound. For example, py_call(m:7, R).