friendlysam.opt.Variable.evaluate

Variable.evaluate(replace=None, evaluators=None)

Evaluate a variable.

See Operation.evaluate() for a general explanation of expression evaluation.

A Variable is evaluated with the following priority order:

  1. If it has a value, that is returned.

2. Otherwise, if the variable is a key in the replace dictionary, the corresponding value is returned.

  1. Otherwise, the variable itself is returned.
Parameters:
  • replace (dict, optional) – Replacements.
  • evaluators (dict, optional) – Has no effect. Just included to be compatible with the signature of Operation.evaluate().

Examples

>>> x = Variable('x')
>>> x.evaluate() == x
True
>>> x.evaluate({x: 5}) == 5
True

>>> x.value = -1
>>> x.evaluate() == -1
True
>>> x.evaluate({x: 5}) == -1 # .value goes first!
True

>>> del x.value
>>> x.value
Traceback (most recent call last):
...
friendlysam.opt.NoValueError