2*x + y + 1
"""
if expression is None:
- if isinstance(symbol, Mapping):
- symbol = symbol.items()
- substitutions = symbol
+ substitutions = dict(symbol)
else:
- substitutions = [(symbol, expression)]
- result = self
- for symbol, expression in substitutions:
+ substitutions = {symbol: expression}
+ for symbol in substitutions:
if not isinstance(symbol, Symbol):
raise TypeError('symbols must be Symbol instances')
- coefficients = [(othersymbol, coefficient)
- for othersymbol, coefficient in result._coefficients.items()
- if othersymbol != symbol]
- coefficient = result._coefficients.get(symbol, 0)
- constant = result._constant
- result = LinExpr(coefficients, constant) + coefficient*expression
+ result = self._constant
+ for symbol, coefficient in self._coefficients.items():
+ expression = substitutions.get(symbol, symbol)
+ result += coefficient * expression
return result
@classmethod