Expression

class gamspy.Expression(left: OperableType | ImplicitEquation | str | None, operator: str, right: OperableType | str | None)

Bases: Operable

Represents an expression involving two operands and an operator.

This class constructs a binary expression tree that can be evaluated or translated into GAMS syntax.

Parameters:

leftOperableType | ImplicitEquation | None

Left operand.

operatorstr

The operator symbol (e.g., ‘+’, ‘-’, ‘*’, ‘=’, ‘eq’).

rightOperableType | str | None

Right operand.

Attributes:

records

Evaluates the expression and returns the resulting records.

representation

Methods

gamsRepr()	Representation of this Expression in GAMS language.
getDeclaration()	Declaration of the Expression in GAMS
latexRepr()	Returns the LaTeX representation of this Expression.
toGraph()	Return a graphviz.Digraph of this expression's tree.
toList()	Convenience method to return the records of the expression as a list.
toValue()	Convenience method to return expression records as a Python float.

Examples

>>> import gamspy as gp
>>> m = gp.Container()
>>> a = gp.Parameter(m, name="a")
>>> b = gp.Parameter(m, name="b")
>>> expression = a * b
>>> expression.gamsRepr()
'a * b'

gamsRepr() → str

Representation of this Expression in GAMS language.

Returns:

str

Examples

>>> import gamspy as gp
>>> m = gp.Container()
>>> a = gp.Parameter(m, name="a")
>>> b = gp.Parameter(m, name="b")
>>> expression = a * b
>>> expression.gamsRepr()
'a * b'

getDeclaration() → str

Declaration of the Expression in GAMS

Returns:

str

Examples

>>> import gamspy as gp
>>> m = gp.Container()
>>> a = gp.Parameter(m, name="a")
>>> b = gp.Parameter(m, name="b")
>>> expression = a * b
>>> expression.getDeclaration()
'a * b'

latexRepr() → str

Returns the LaTeX representation of this Expression.

Returns:

str

The LaTeX string.

Examples

>>> import gamspy as gp
>>> m = gp.Container()
>>> a = gp.Parameter(m, name="a")
>>> b = gp.Parameter(m, name="b")
>>> (a + b).latexRepr()
'a + b'

toGraph()

Return a graphviz.Digraph of this expression’s tree.

Each operator/operation is drawn as a box and each symbol or number as a leaf, so the structure of the expression can be inspected visually or rendered to a file. Requires the optional graphviz dependency (pip install gamspy[graph]); a ValidationError is raised if it is not installed.

Returns:

graphviz.Digraph

Examples

>>> import gamspy as gp
>>> m = gp.Container()
>>> a = gp.Parameter(m, name="a")
>>> b = gp.Parameter(m, name="b")
>>> c = gp.Parameter(m, name="c")
>>> d = gp.Parameter(m, name="d")
>>> graph = (a * b + c / d).toGraph()
>>> graph.render("expr", format="svg")

toList() → list

Convenience method to return the records of the expression as a list.

Returns:

list

Examples

>>> import numpy as np
>>> import gamspy as gp
>>> m = gp.Container()
>>> i = gp.Set(m, records=range(3))
>>> a = gp.Parameter(m, domain=i, records=np.array([1,2,3]))
>>> b = gp.Parameter(m, domain=i, records=np.array([4,5,6]))
>>> (a + b).toList()
[['0', 5.0], ['1', 7.0], ['2', 9.0]]

toValue() → float

Convenience method to return expression records as a Python float. Only possible if there is a single record as a result of the expression evaluation.

Returns:

float | None

Raises:

TypeError

In case the dimension of the expression is not zero.

Examples

>>> import gamspy as gp
>>> m = gp.Container()
>>> a = gp.Parameter(m, records=5)
>>> b = gp.Parameter(m, records=6)
>>> (a + b).toValue()
np.float64(11.0)

property records: pd.DataFrame | None

Evaluates the expression and returns the resulting records.

Returns:

pd.DataFrame | None

Examples

>>> import gamspy as gp
>>> m = gp.Container()
>>> a = gp.Parameter(m, records=5)
>>> b = gp.Parameter(m, records=6)
>>> (a + b).records
   value
0   11.0

property representation: str

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