Components¶

Variable¶

class epyglpki.Variable¶

One of the problem’s variables

bounds(lower, upper)¶

Change or retrieve variable bounds

Parameters:	lower (`Real` or `False`) – the variable’s lower bound (`False` to remove bound; omit for retrieval only) upper (`Real` or `False`) – the variable’s upper bound (`False` to remove bound; omit for retrieval only)
Returns:	the variable’s bounds
Return type:	length-2 `tuple` of `float` (or `False`)
Raises:	TypeError – if lower or upper is not `Real` or `False` ValueError – if lower is larger than upper

>>> p = MILProgram()
>>> x = p.add_variable()
>>> x.bounds()
(False, False)
>>> x.bounds(lower=0, upper=5.5)
(0.0, 5.5)
>>> x.bounds(upper=False)
(0.0, False)

coeffs(coeffs)¶

Change or retrieve variable coefficients (constraint matrix column)

Parameters:	coeffs (`Mapping` of `Constraint` to `Real`) – the mapping with coefficients to change ({} to set all coefficients to 0; omit for retrieval only)
Returns:	the coefficient mapping, which only contains nonzero coefficients
Return type:	`dict` of `Constraint` to `float`
Raises:	TypeError – if coeffs is not `Mapping` TypeError – if a coefficient key is not `Variable` TypeError – if a coefficient value is not `Real`

>>> p = MILProgram()
>>> c = p.add_constraint()
>>> d = p.add_constraint()
>>> x = p.add_variable()
>>> x.coeffs()
{}
>>> x.coeffs({c: 10/9, d: 0})
{<epyglpki.Constraint object at 0x...>: 1.1111...}
>>> x.coeffs({})
{}

kind(kind)¶

Change or retrieve variable kind

Raises ValueError:
Parameters:	kind (`str`, either `'continuous'`, `'integer'`, or `'binary'`) – the new variable kind (omit for retrieval only)
Returns:	the variable kind
Return type:	`str`
	if kind is not `'continuous'`, `'integer'`, or `'binary'`

>>> p = MILProgram()
>>> x = p.add_variable()
>>> x.kind()
'continuous'
>>> x.kind('integer')
'integer'

Note

A variable has 'binary' kind if and only if it is an integer variable with lower bound zero and upper bound one:

>>> x.kind()
'integer'
>>> x.bounds(lower=0, upper=1)
(0.0, 1.0)
>>> x.kind()
'binary'
>>> x.bounds(upper=3)
(0.0, 3.0)
>>> x.kind()
'integer'
>>> x.kind('binary')
'binary'
>>> x.bounds()
(0.0, 1.0)

name(name)¶

Change or retrieve variable name

Parameters:	name (`str`) – the new variable name (omit for retrieval only)
Returns:	the variable name
Return type:	`str`
Raises:	TypeError – if name is not a `str` ValueError – if name exceeds 255 bytes encoded in UTF-8

>>> p = MILProgram()
>>> x = p.add_variable()
>>> x.name()
''
>>> x.name('Stake')
'Stake'
>>> x.name()
'Stake'

remove()¶

Remove the variable from the problem

>>> p = MILProgram()
>>> x = p.add_variable()
>>> p.variables()
[<epyglpki.Variable object at 0x...>]
>>> x.remove()
>>> p.variables()
[]

Note

Removing a variable from a problem object does not delete the referencing Variable objects, which in some sense become ‘zombie’ objects; they should best be deleted manually:

>>> p.variables()
[]
>>> x
<epyglpki.Variable object at 0x...>
>>> x.name()
Traceback (most recent call last):
  ...
ValueError: <epyglpki.Variable object at 0x...> is not in list

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  ...
IndexError: This is possibly a zombie; kill it using 'del'.
>>> del x
>>> x
Traceback (most recent call last):
  ...
NameError: name 'x' is not defined

Constraint¶

class epyglpki.Constraint¶

One of the problem’s constraints

bounds(lower, upper)¶

Change or retrieve constraint bounds

Parameters:	lower (`Real` or `False`) – the constraint’s lower bound (`False` to remove bound; omit for retrieval only) upper (`Real` or `False`) – the constraint’s upper bound (`False` to remove bound; omit for retrieval only)
Returns:	the constraint’s bounds
Return type:	length-2 `tuple` of `float` (or `False`)
Raises:	TypeError – if lower or upper is not `Real` or `False` ValueError – if lower is larger than upper

>>> p = MILProgram()
>>> c = p.add_constraint()
>>> c.bounds()
(False, False)
>>> c.bounds(lower=-1/2, upper=1/2)
(-0.5, 0.5)
>>> c.bounds(lower=False)
(False, 0.5)

coeffs(coeffs)¶

Change or retrieve constraint coefficients (constraint matrix row)

Parameters:	coeffs (`Mapping` of `Variable` to `Real`) – the mapping with coefficients to change ({} to set all coefficients to 0; omit for retrieval only)
Returns:	the coefficient mapping, which only contains nonzero coefficients
Return type:	`dict` of `Variable` to `float`
Raises:	TypeError – if coeffs is not `Mapping` TypeError – if a coefficient key is not `Variable` TypeError – if a coefficient value is not `Real`

>>> p = MILProgram()
>>> x = p.add_variable()
>>> y = p.add_variable()
>>> c = p.add_constraint()
>>> c.coeffs()
{}
>>> c.coeffs({x: .5, y: 0})
{<epyglpki.Variable object at 0x...>: 0.5}
>>> c.coeffs({})
{}

name(name)¶

Change or retrieve constraint name

Parameters:	name (`str`) – the new constraint name (omit for retrieval only)
Returns:	the constraint name
Return type:	`str`
Raises:	TypeError – if name is not a `str` ValueError – if name exceeds 255 bytes encoded in UTF-8

>>> p = MILProgram()
>>> c = p.add_constraint()
>>> c.name()
''
>>> c.name('Budget')
'Budget'
>>> c.name()
'Budget'

remove()¶

Remove the constraint from the problem

>>> p = MILProgram()
>>> c = p.add_constraint()
>>> p.constraints()
[<epyglpki.Constraint object at 0x...>]
>>> c.remove()
>>> p.constraints()
[]

Note

Removing a constraint from a problem object does not delete the referencing Constraint objects, which in some sense become ‘zombie’ objects; they should best be deleted manually:

>>> p.constraints()
[]
>>> c
<epyglpki.Constraint object at 0x...>
>>> c.name()
Traceback (most recent call last):
  ...
ValueError: <epyglpki.Constraint object at 0x...> is not in list

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  ...
IndexError: This is possibly a zombie; kill it using 'del'.
>>> del c
>>> c
Traceback (most recent call last):
  ...
NameError: name 'c' is not defined

Objective¶

class epyglpki.Objective¶

The problem’s objective function

coeffs(coeffs)¶

Change or retrieve objective function coefficients

Parameters:	coeffs (`Mapping` of `Variable` to `Real`) – the mapping with coefficients to change ({} to set all coefficients to 0 ; omit for retrieval only)
Returns:	the coefficient mapping, which only contains nonzero coefficients
Return type:	`dict` of `Variable` to `float`
Raises:	TypeError – if coeffs is not `Mapping` TypeError – if a coefficient key is not `Variable` TypeError – if a coefficient value is not `Real`

>>> p = MILProgram()
>>> x = p.add_variable()
>>> y = p.add_variable()
>>> o = p.objective()
>>> o.coeffs()
{}
>>> o.coeffs({x: 3, y: 0})
{<epyglpki.Variable object at 0x...>: 3.0}
>>> o.coeffs({})
{}

constant(constant)¶

Change or retrieve objective function constant

Raises TypeError:
Parameters:	constant (`Real`) – the new objective function constant (omit for retrieval only)
Returns:	the objective function constant
Return type:	`float`
	if constant is not `Real`

>>> p = MILProgram()
>>> o = p.objective()
>>> o.constant()
0.0
>>> o.constant(3)
3.0

direction(direction)¶

Change or retrieve objective direction

Raises ValueError:
Parameters:	direction (`str`, either `'minimize'` or `'maximize'`) – the new objective direction (omit for retrieval only)
Returns:	the objective direction
Return type:	`str`
	if direction is not `'minimize'` or `'maximize'`

>>> p = MILProgram()
>>> o = p.objective()
>>> o.direction()
'minimize'
>>> o.direction('maximize')
'maximize'

name(name)¶

Change or retrieve objective function name

Parameters:	name (`str`) – the new objective function name (omit for retrieval only)
Returns:	the objective function name
Return type:	`str`
Raises:	TypeError – if name is not a `str` ValueError – if name exceeds 255 bytes encoded in UTF-8

>>> p = MILProgram()
>>> o = p.objective()
>>> o.name()
''
>>> o.name('σκοπός')
'σκοπός'
>>> o.name()
'σκοπός'

Components¶

Variable¶

Constraint¶

Objective¶

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Variable¶

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Objective¶

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