cirq.CircuitDag.pred

CircuitDag.pred

Graph adjacency object holding the predecessors of each node.

This object is a read-only dict-like structure with node keys

and neighbor-dict values. The neighbor-dict is keyed by neighbor

to the edge-data-dict. So G.pred[2][3]['color'] = 'blue' sets

the color of the edge (3, 2) to "blue".

Iterating over G.pred behaves like a dict. Useful idioms include

for nbr, datadict in G.pred[n].items():. A data-view not provided

by dicts also exists: for nbr, foovalue in G.pred[node].data('foo'):

A default can be set via a default argument to the data method.