Create an expression from a string. Raise SyntaxError if the string is
not properly formatted.
"""
- # add implicit multiplication operators, e.g. '5x' -> '5*x'
+ # Add implicit multiplication operators, e.g. '5x' -> '5*x'.
string = LinExpr._RE_NUM_VAR.sub(r'\1*\2', string)
tree = ast.parse(string, 'eval')
expr = cls._fromast(tree)
if symbol == sympy.S.One:
constant = coefficient
elif isinstance(symbol, sympy.Dummy):
- # we cannot properly convert dummy symbols
+ # We cannot properly convert dummy symbols with respect to
+ # symbol equalities.
raise TypeError('cannot convert dummy symbols')
elif isinstance(symbol, sympy.Symbol):
symbol = Symbol(symbol.name)
Two instances of Symbol are equal if they have the same name.
"""
+ __slots__ = (
+ '_name',
+ '_constant',
+ '_symbols',
+ '_dimension',
+ )
+
def __new__(cls, name):
"""
Return a symbol with the name string given in argument.
raise SyntaxError('invalid syntax')
self = object().__new__(cls)
self._name = name
- self._coefficients = {self: Fraction(1)}
self._constant = Fraction(0)
self._symbols = (self,)
self._dimension = 1
return self
+ @property
+ def _coefficients(self):
+ # This is not implemented as an attribute, because __hash__ is not
+ # callable in __new__ in class Dummy.
+ return {self: Fraction(1)}
+
@property
def name(self):
"""
"""
if name is None:
name = 'Dummy_{}'.format(Dummy._count)
- elif not isinstance(name, str):
- raise TypeError('name must be a string')
- self = object().__new__(cls)
+ self = super().__new__(cls, name)
self._index = Dummy._count
- self._name = name.strip()
- self._coefficients = {self: Fraction(1)}
- self._constant = Fraction(0)
- self._symbols = (self,)
- self._dimension = 1
Dummy._count += 1
return self
fractions.Fraction classes.
"""
+ __slots__ = (
+ '_coefficients',
+ '_constant',
+ '_symbols',
+ '_dimension',
+ ) + Fraction.__slots__
+
def __new__(cls, numerator=0, denominator=None):
self = object().__new__(cls)
self._coefficients = {}