Class janus.query() is
similar to the
janus.query_once()
function, but it returns a Python
iterator that allows for iterating over the answers to a
non-deterministic Prolog predicate.
The iterator also implements the Python context manaager protocol
(for the Python with statement).
- query janus.query(query,
inputs={}, keep=False)
- As janus.query_once(),
returning an iterator that provides an answer dict as janus.query_once()
for each answer to query. Answers never have
truth False.
See discussion above.
- Compatibility
- PIP. The
keep is a SWI-Prolog extension.
- Query janus.Query(query,
inputs={}, keep=False)
- Deprecated. This class was renamed to janus.query(.)
- dict
|None janus.query.next() - Explicitly ask for the next solution of the iterator. Normally, using
the
query as an iterator is to be preferred. See discussion
above. q.next() is equivalent to next(q)
except it returns None if there are no more values instead
of raising the StopIteration exception.
- None janus.query.close()
- Close the query. Closing a query is obligatory. When used as an
iterator, the Python destructor (__del__()) takes care of closing
the query. However, Python does not guarantee when the destructor will
be called, so it is recommended that the context manager protocol is
used (with the Python
with statement), which closes the
query when the query goes out of scope or when an error happens.
- Compatibility
- PIP.
