LpConstraint no longer inherits from LpAffineExpression -> no longer has addterm method. How to now add terms?

[simon-b]

I have a code-base where I often use constraint.addterm(variable, coefficient) to modify specific constraints. Now, this is not available because this method was inherited from LpAffineExpression, and is not replaced after changes introduced by #5e5ca199fa02075d3d1e27778b45130a13f3fe2e.

What is the recommended approach to add terms to constraints now?

[pchtsp]

@MBradbury may know this one

[MBradbury]

My advice would be to treat the constraint as immutable, if you need to change it you can do:

x = LpVariable("x")
y = LpVariable("y")
constraint = x + y <= 5
constraint2 = constraint + x
assert str(constraint2) == str(2*x + y <= 5)
assert constraint is not constraint2
assert constraint.expr is not constraint2.expr

If you really want to modify the constraint with addterm, just access the underlying LpAffineExpression:

constraint = x + y <= 5
constraint.expr.addterm(x, 1)
assert str(constraint2) == str(2*x + y <= 5)

addterm really seems like an implementation detail, so really should be avoided. For example, LpAffineExpression.addInPlace is much more flexible. Also addInPlace is implemented for constraints.

constraint = x + y <= 5
constraint.addInPlace(1*x)
assert str(constraint2) == str(2*x + y <= 5)

@pchtsp I think making addterm private by renaming to _addterm would be sensible.