# Size of a single page in a paginated query.
_PAGE_SIZE = 100
[docs]class PaginatedCollection:
""" An iterable collection of database objects (Projects, Labels, etc...).
Implements automatic (transparent to the user) paginated fetching during
iteration. Intended for use by library internals and not by the end user.
For a list of attributes see __init__(...) documentation. The params of
__init__ map exactly to object attributes.
"""
[docs] def __init__(self, client, query, params, dereferencing, obj_class):
""" Creates a PaginatedCollection.
Args:
client (labelbox.Client): the client used for fetching data from DB.
query (str): Base query used for pagination. It must contain two
'%d' placeholders, the first for pagination 'skip' clause and
the second for the 'first' clause.
params (dict): Query parameters.
dereferencing (iterable): An iterable of str defining the keypath
that needs to be dereferenced in the query result in order to
reach the paginated objects of interest.
obj_class (type): The class of object to be instantiated with each
dict containing db values.
"""
self.client = client
self.query = query
self.params = params
self.dereferencing = dereferencing
self.obj_class = obj_class
self._fetched_pages = 0
self._fetched_all = False
self._data = []
self._data_ind = 0
def __iter__(self):
self._data_ind = 0
return self
def __next__(self):
if len(self._data) <= self._data_ind:
if self._fetched_all:
raise StopIteration()
query = self.query % (self._fetched_pages * _PAGE_SIZE, _PAGE_SIZE)
self._fetched_pages += 1
results = self.client.execute(query, self.params)
for deref in self.dereferencing:
results = results[deref]
page_data = [
self.obj_class(self.client, result) for result in results
]
self._data.extend(page_data)
if len(page_data) < _PAGE_SIZE:
self._fetched_all = True
if len(page_data) == 0:
raise StopIteration()
rval = self._data[self._data_ind]
self._data_ind += 1
return rval