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class `QuadraticExpression`(quadratic_program, coefficients)[source]

Bases: `qiskit_optimization.problems.quadratic_program_element.QuadraticProgramElement`

Representation of a quadratic expression by its coefficients.

The quadratic expression can be defined via an array, a list, a sparse matrix, or a dictionary that uses variable names or indices as keys and stores the values internally as a dok_matrix. We stores values in a compressed way, i.e., values at symmetric positions are summed up in the upper triangle. For example, {(0, 1): 1, (1, 0): 2} -> {(0, 1): 3}.

Parameters
• quadratic_program (`Any`) – The parent QuadraticProgram.

• coefficients (`Union`[`ndarray`, `spmatrix`, `List`[`List`[`float`]], `Dict`[`Tuple`[`Union`[`int`, `str`], `Union`[`int`, `str`]], `float`]]) – The (sparse) representation of the coefficients.

Attributes

 `bounds` Returns the lower bound and the upper bound of the quadratic expression `coefficients` Returns the coefficients of the quadratic expression.

Methods

 Returns the coefficient where i, j can be a variable names or indices. Evaluate the quadratic expression for given variables: x * Q * x. Evaluate the gradient of the quadratic expression for given variables. `to_array`([symmetric]) Returns the coefficients of the quadratic expression as array. `to_dict`([symmetric, use_name]) Returns the coefficients of the quadratic expression as dictionary, either using tuples of variable names or indices as keys.