tensor.py 文件源码

def contract_internal(self, label1, label2, index1=0, index2=0):
        """By default will contract the first index with label1 with the 
        first index with label2. index1 and index2 can be specified to contract
        indices that are not the first with the specified label."""

        label1_indices = [i for i, x in enumerate(self.labels) if x == label1]
        label2_indices = [i for i, x in enumerate(self.labels) if x == label2]

        index_to_contract1 = label1_indices[index1]
        index_to_contract2 = label2_indices[index2]

        self.data = np.trace(self.data, axis1=index_to_contract1, axis2=
        index_to_contract2)

        # The following removes the contracted indices from the list of labels
        self.labels = [label for j, label in enumerate(self.labels)
                       if j not in [index_to_contract1, index_to_contract2]]

    # aliases for contract_internal