Python巧妙实现Fibonacci序列算法

 

# Fibonacci number series
# tested with Python24       vegaseat      18oct2005

def fibonacci():
    """a generator for Fibonacci numbers, goes to next number in series on each call"""
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b

f = fibonacci()
for x in range(13):
    print f.next(),  # 0 1 1 2 3 5 8 13 21 34 55 89 144

print
   
def fibo(n):
    """
    use recursion to get Fibonacci numbers, returns the Fibonacci value for n
    not very efficient because of the many function calls
    """
    if n < 2:
        return n
    else:
        return fibo(n - 1) + fibo(n - 2)

for x in range(13):
    print "fibo(%d) = %d" % (x, fibo(x))
   
print
print "Calculating ..."
print

print "fibo(%d) = %d" % (30, fibo(30))  # this takes a moment!