# -*- coding: utf-8 -*-
from pybel.constants import FUNCTION
__all__ = [
'get_leaves_by_type',
]
[docs]def get_leaves_by_type(graph, func=None, prune_threshold=1):
"""Returns an iterable over all nodes in graph (in-place) with only a connection to one node. Useful for gene and
RNA. Allows for optional filter by function type.
:param pybel.BELGraph graph: A BEL graph
:param func: If set, filters by the node's function from :mod:`pybel.constants` like
:data:`pybel.constants.GENE`, :data:`pybel.constants.RNA`, :data:`pybel.constants.PROTEIN`, or
:data:`pybel.constants.BIOPROCESS`
:type func: str
:param prune_threshold: Removes nodes with less than or equal to this number of connections. Defaults to :code:`1`
:type prune_threshold: int
:return: An iterable over nodes with only a connection to one node
:rtype: iter[tuple]
"""
for node, data in graph.nodes(data=True):
if func and func != data.get(FUNCTION):
continue
if graph.in_degree(node) + graph.out_degree(node) <= prune_threshold:
yield node