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# gurobipy.Column

class Column

  Gurobi column object. A column consists of a list of coefficient, constraint pairs. Columns are used to represent the set of constraints in which a variable participates, and the associated coefficients. They are temporary objects that typically have short lifespans.

  You generally build columns using the `Column` constructor. Terms can be added to an existing column using `addTerms`. Terms can also be removed from a column using `remove`.

  Individual terms in a column can be queried using the `getConstr`, and `getCoeff` methods. You can query the number of terms in the column using the `size` method.

  Column(coeffs=None, constrs=None)

    Column constructor.

    Parameters:

      - coeffs – (optional) Lists the coefficients associated with the members of `constrs`.

      - constrs – (optional) Constraint or constraints that participate in expression. If `constrs` is a list, then `coeffs` must contain a list of the same length. If `constrs` is a single constraint, then `coeffs` must be a scalar.

    Returns:

      An expression object.

    Example:

          constrs = model.getConstrs()

          c = Column()
          c.addTerms(3.0, constrs[0])
          model.addVar(vtype=GRB.BINARY, obj=1.0, column=c)

          model.addVar(vtype=GRB.INTEGER, column=Column(3.0, constrs[0]))

          model.addVar(obj=3.0, column=Column([1.0, 2.0], constrs[1:3]))

  addTerms(coeffs, constrs)

    Add new terms into a column.

    Parameters:

      - coeffs – Coefficients for added constraints; either a list of coefficients or a single coefficient. The two arguments must have the same size.

      - constrs – Constraints to add to column; either a list of constraints or a single constraint. The two arguments must have the same size.

    Example:

          col.addTerms(1.0, x)
          col.addTerms([2.0, 3.0], [y, z])

  clear()

    Remove all terms from a column.

    Example:

          col.clear()

  copy()

    Copy a column.

    Returns:

      Copy of input column.

    Example:

          col0 = Column(1.0, c0)
          col1 = col0.copy()

  getCoeff(i)

    Retrieve the coefficient from a single term in the column.

    Returns:

      Coefficient for the term at index `i` in the column.

    Example:

          col = Column([1.0, 2.0], [c0, c1])
          print(col.getCoeff(1))

  getConstr(i)

    Retrieve the constraint object from a single term in the column.

    Returns:

      Constraint for the term at index `i` in the column.

    Example:

          col = Column([1.0, 2.0], [c0, c1])
          print(col.getConstr(1))

  remove(item)

    Remove a term from a column.

    Parameters:

      item – If `item` is an integer, then the term stored at index `item` of the column is removed. If `item` is a Constr, then all terms that involve `item` are removed.

    Example:

          col = Column([1.0, 2.0], [c0, c1])
          col.remove(c0)

  size()

    Retrieve the number of terms in the column.

    Returns:

      Number of terms in the column.

    Example:

          print(Column([1.0, 2.0], [c0, c1]).size())

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