def __bool__(self):
"""Coerce the value to a bool
Numeric values can be coerced to bool only if the value /
expression is constant. Fixed (but non-constant) or variable
values will raise an exception.
Raises:
PyomoException
"""
# Note that we want to implement __bool__, as scalar numeric
# components (e.g., Param, Var) implement __len__ (since they
# are implicit containers), and Python falls back on __len__ if
# __bool__ is not defined.
if self.is_constant():
return bool(self())
raise PyomoException("""
Cannot convert non-constant Pyomo numeric value (%s) to bool.
This error is usually caused by using a Var, unit, or mutable Param in a
Boolean context such as an "if" statement. For example,
>>> m.x = Var()
>>> if not m.x:
... pass
would cause this exception.""".strip() % (self, ))
def solve(self, model, timer: HierarchicalTimer = None):
avail = self.available()
if not avail:
raise PyomoException(
f'Solver {self.__class__} is not available ({avail}).')
if self._last_results_object is not None:
self._last_results_object.solution_loader.invalidate()
if timer is None:
timer = HierarchicalTimer()
try:
TempfileManager.push()
if self.config.filename is None:
self._filename = TempfileManager.create_tempfile()
else:
self._filename = self.config.filename
TempfileManager.add_tempfile(self._filename + '.lp', exists=False)
TempfileManager.add_tempfile(self._filename + '.log', exists=False)
timer.start('write lp file')
self._writer.write(model, self._filename + '.lp', timer=timer)
timer.stop('write lp file')
res = self._apply_solver(timer)
self._last_results_object = res
if self.config.report_timing:
logger.info('\n' + str(timer))
return res
finally:
# finally, clean any temporary files registered with the
# temp file manager, created/populated *directly* by this
# plugin.
TempfileManager.pop(remove=not self.config.keepfiles)
if not self.config.keepfiles:
self._filename = None
def __bool__(self):
if not self.is_constant():
raise PyomoException('Cannot convert non-constant expression '
'to bool. This error is usually caused by '
'using an expression in a boolean context '
'such as an if statement. For example, \n'
' m.x = Var()\n'
' if m.x <= 0:\n'
' ...\n'
'would cause this exception.')
return bool(self())
def __bool__(self):
if self.is_constant():
return bool(self())
raise PyomoException("""
Cannot convert non-constant Pyomo expression (%s) to bool.
This error is usually caused by using a Var, unit, or mutable Param in a
Boolean context such as an "if" statement, or when checking container
membership or equality. For example,
>>> m.x = Var()
>>> if m.x >= 1:
... pass
and
>>> m.y = Var()
>>> if m.y in [m.x, m.y]:
... pass
would both cause this exception.""".strip() % (self, ))