Hello again I think my question got lost in all the others raised, so here I am again :P
So, I tried my best, was looking into the eval and exec function, but still no succsess.. Maybe it helps when I provide the code I want to implement: def newton_verfahren(self): if self.cB_1.currentText() == 'Newton': x0 = self.newton_x.text() f1 = self.func_1.text() f2 = self.func_2.text() tol = self.newton_tol.text() n = self.newton_n.text() k = Numerik_Funktionen.newton(int(x0), eval(f1), eval(f2), int(tol), int(n)) k1 = str(k[0]) k2 = str(k[1]) k3 = str(k[2]) self.ausgabe.setText('Startwert -> x0: '+ k1 + "\n" + 'Anzahl Iterationen: ' + k2 +"\n" + 'f(x~): ' + k3) Notice that cB_1 is a combobox, newton_x, func_1, func_2, newton_tol and newton_n are all QLineEdits. The code above doesn't work, so I've opend a 'test' file to just play around with the functions. Withs test, this return a correct value for the two x functions: from sympy import symbols x = symbols('x') f1 = eval(input('function 1 ')) f2 = eval(input('function 2 ')) But now I get and error from the imported module in the line where the abs(f(x)) > tol. It states that the 'Pow' object is not callable. And now I don't know how to proceed, I can't figure out a way to make the call to the imported module: x = symbols('x') def newton(x0, f, fx, tol, n = 20000): ''' Näherung zur lösung einer Gleichung mit dem Newton-Verfahren x0 = Startwert f = zu lösende Funktion fx = Ableitung der Funktion ''' x = x0 k = 0 while n > k and abs(f(x)) > tol: k += 1 x = x - f(x)/fx(x) print('x', k, '\n', x) print('Startwert -> x0', '\n', x0) print('Anzahl Iterationen', '\n', k) print('f(x~)', '\n', f(x)) print('Näherungswert -> x~', '\n', x) return x0, k, f(x), x Regards Nicco -- https://mail.python.org/mailman/listinfo/python-list