user input string to function

[Nico Vogeli]

Am Montag, 25. Dezember 2017 15:58:26 UTC+1 schrieb Chris Angelico:
> On Tue, Dec 26, 2017 at 1:48 AM, Nico Vogeli <nicco.9537 at gmail.com> wrote:
> > Am Montag, 25. Dezember 2017 14:51:21 UTC+1 schrieb Chris Angelico:
> >> On Tue, Dec 26, 2017 at 12:36 AM, Nico Vogeli <nicco.9537 at gmail.com> wrote:
> >> > Hi everybody. First ad foremost, happy Christmas!
> >>
> >> Same to you!
> >>
> >> > I want to let the use input a function (like x**2) and parse it after that through code (for my numeric class)
> >> >
> >> > def newton(x0, s, s2, tol, n = 20000):
> >> >     '''
> >> >     Näherung zur lösung einer Gleichung mit dem Newton-Verfahren
> >> >     x0 = Startwert
> >> >     f = zu lösende Funktion
> >> >     fx = Ableitung der Funktion
> >> >
> >> >     '''
> >> >     def f(a):
> >> >         y = s
> >> >         return y
> >> >
> >> >     def fx(a):
> >> >         y = s2
> >> >         return y
> >>
> >>
> >> > newton(2, 3*x**2, 6*x, 0.1, 2)
> >> >
> >> > I notice that the x is not converted to an integer, because of the x = symplos('x')
> >> > But I don't know how I could possibli change the code to work...
> >>
> >> The easiest way is to pass a *function* to newton(). It'd look like this:
> >>
> >> def newton(x0, f, fx, tol, n=20000):
> >>     ... as before, but without the nested functions
> >>
> >> newton(2, lambda x: 3*x**2, lambda x: 6*x, 0.1, 2)
> >>
> >> At least, I think that's how you're doing things. Inside the nested
> >> functions, you use 'a', but outside, you use 'x'. Are those
> >> representing the same concept? If so, the lambda functions given here
> >> will have the same effect.
> >>
> >> Hope that helps!
> >>
> >> ChrisA
> >
> > Hi Chris
> >
> > Thanks very much for your quick response!
> > I was in a bit of a rush, so I confused the variables (don't worry, I just messed arround to try different things, the original code was al tidy with the variable).
> >
> > I tried your input, but now I get another error:
> >
> >
> >   File "C:/Users/Nicco ZHAW/Desktop/Test GUI/Test Projekt.py", line 42, in newton
> >     b = x - f(x)/fx(x)
> >
> > TypeError: unsupported operand type(s) for /: 'function' and 'function'
> >
> > This did not occure befor I tried to implement the user input..
> 
> Did you remove the nested functions? The lambda functions completely
> replace your "def f(a)" and "def fx(a)" functions.
> 
> ChrisA

I am so so sorry!! I just did not know what you meant by sested functions.. :P

Thank you so much for helping me! You're great!

Cheers and all the best!

Nicco