我不明白为什么这个python函数返回无,如果它递归调用自己。递归返回无Python函数
这是我解决项目欧拉问题的一部分。无论如何,我已经以更好的方式解决了这个问题,但是这仍然让我很烦恼,因为这个函数似乎可以正常工作 - 而且它似乎知道我想要返回的变量的值。
def next_prime(previous):
if previous % 2 == 0:
candidate = previous + 1
else:
candidate = previous + 2
print "trying", candidate
prime = True
for div in range(2,candidate//2,1):
if candidate % div == 0:
prime = False
print candidate, "is not prime - divisible by", div
next_prime(candidate)
break
if prime is True:
print candidate, "is prime"
#return candidate
last = 896576
print "After", last, ", the next prime is..."
next_prime(last)
这给:
After 896576 , the next prime is...
trying 896577
896577 is not prime - divisible by 3
trying 896579
896579 is not prime - divisible by 701
trying 896581
896581 is not prime - divisible by 7
trying 896583
896583 is not prime - divisible by 3
trying 896585
896585 is not prime - divisible by 5
trying 896587
896587 is prime
但是,如果我去掉了return语句,如果第一次尝试是素数只返回一个值,否则返回无。
你没有使用递归调用的值,这是正常的吗? – Tobu 2010-01-17 21:10:44