Das deutsche Python-Forum

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    def next(self):
        if str(self.a + self.b)[-1] == "L":
            return ...
        self.a, self.b = self.b, self.a + self.b
        return self.a

    def previous(self):
        if self.b == 1:
            return ...
        self.a, self.b = self.b - self.a, self.a
        return self.a

Code: Alles auswählen

class FibonacciIterator(object):
    def __init__(self):
        self.a = self.b = 1

    def next(self):
        self.a, self.b = self.b, self.a + self.b
        return self.a

    def previous(self):
        self.a, self.b = self.b - self.a, self.a
        return self.a

    def __str__(self):
        return "{} {}".format(self.a, self.b)


def main():
    fibonacci_sequence = FibonacciIterator()
    print fibonacci_sequence.a

    for i in xrange(10):
        print i, fibonacci_sequence.next()
   
    print fibonacci_sequence.a
 
    for i in reversed(xrange(9)):
        print i, fibonacci_sequence.previous()
   
    try:
        fibonacci_sequence.previous()
    except Exception as error:
        assert isinstance(error, StopIteration)

if __name__ == "__main__":
    main()

Code: Alles auswählen

try:
    fibonacci_sequence.previous()
except Exception as error:
    assert isinstance(error, StopIteration)

Code: Alles auswählen

         for x in xrange(rabbits):
            label = tk.Label(self.root, image=self.img)
            label.place(x=randint(1, 400), y=randint(1, 400))
            self.hasen.append(label)