这个是短路运算，在或运算中，一个为true结果就为true,a = 'python'print 'hello,', a or 'world'a已经为true,所以or 'word'就不再看了，此时a or 'world'就等价于'python'b = ' 'print 'hello,', b or 'world'b为空值，所以要看or 'word',此时b or 'world'等价于'word'
def square_of_sum(L):
sum = 0
n=1
i=len(L)
while n<=i:
for x in L:
sum+=x**2
n+=1
return sum
print (square_of_sum([1,2,3,4,5]) )
print (square_of_sum([-5,0,5,15,25]))
