斐波那契数列是由 0, 1, 1, 2, 3, 5, 8...构成
请编写一个Fib类，Fib(10)表示数列的前10个元素，print Fib(10) 可以打印出数列的前 10 个元素
list = ['0', '1']
class Fib:
def __init__(self, n):
self.n = n
self.fib = None
def sum(self):
n1 = 0
n2 = 1
a = 3
if self.n == 1:
self.fib = list[0]
elif self.n == 2:
self.fib = list
else:
while a <= self.n:
nn = n1 + n2
list.append('%s' % nn)
self.fib = list
n1 = n2
n2 = nn
a += 1
return self.fib
def __len__(self):
return len(self.fib)
def __getitem__(self, item):
return self.fib[item]
if __name__=="__main__":
a = Fib(10)
print(a.sum())
print(len(a))
print(a[5])
