[EMAIL PROTECTED] escribió: > Hello, > > # the idea is now to give the definition of the multiplication of > functions and integers > # (f * c)(xx) := f(x)*c > [lambda xx: f(xx)*y for y in range(1,5)][0](1) > # returns 4
here lambda uses a variable defined outside of the lambda (y). Any change made to y will be visible within the lambda. In your example the last value for y is 4, so: [...][0](1) = f(1) * 4 = 4 > # I would expect 1*x*x = 1 you should use a local variable to "protect" y: [ lambda xx, y=y : f(xx) * y for y in range(1, 5) ] > # Where is my mistake and what would be the correct way to do this > without lambdas? You can emulate callables http://docs.python.org/ref/callable-types.html class Callable: def __init__(self, f, y) : self.y = y self.f = f def __call__(self, x) : return self.f(x) * self.y f = lambda x : x * x [ Callable(f, y) for y in range(1, 5) ] if you *absolutely* don't want lambdas you can hard code the x*x in __call__ and get rid of self._f, or you can define: class Monomial: def __init__(self, exp, coef) : self.exp = exp self.coef = coef def __call__(self, x) : return x ** self.exp * self.coef [ Monomial(2, y) for y in range(1, 5) ] Another way, somewhat convoluted, using closures: def make_list() : def make_function(y) : def function(x) : return x * x * y return function return [ make_function(y) for i in range(1, 5) ] is essentially the same as lambda. Mostly didactic. HTH -- http://mail.python.org/mailman/listinfo/python-list
