Euler 2项目：正确的答案，但是在cod中有一些困扰我的事情

Question

# Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
# 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
# By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

fibon = [1, 2] # The first 2 numbers in the sequence
addtoend = 0 # The number that will be added to the end of the sequence
evens = [] # Will hold the even numbers in the sequence

while fibon[-1] <= 4000000: # Starts the While loop
    addtoend = fibon[-1] + fibon[-2] # Sets addtoend equal to the last two items in fibon[]
    fibon.append(addtoend) # Appends addtoend onto the end of fibon[]

print fibon # Print out fibon[]

for i in fibon: # Starts the for loop
    if i % 2 == 0: # If the remainder of the current item in the list when divided by 2 is 0...
        evens.append(i) # Then add it to the evens[] list
    else: # Otherwise...
        pass # Just skip it

print evens # Print the evens array, with all the even numbers from fibon[] inside it.
print sum(evens) # Print the sum of all the even numbers from evens[]

结果如下：

^{pr2}$

我在ProjectEuler上检查了答案，结果是正确的，这很好：D但是有一件事我不确定，当它按顺序打印出数字列表时，它的末尾有一个数字：5702887。这已经超过了400万个循环，虽然它不影响整个答案，但我很困惑它是如何存在的。在

提前感谢：D

Answer 1

考虑一下这段代码

while fibon[-1] <= 4000000:
    addtoend = fibon[-1] + fibon[-2] 
    fibon.append(addtoend)

现在考虑一下fibon[-1]包含3524578的情况。由于条件是true，循环将运行，并在序列中添加和追加下一个数字，即5702887。在

现在条件变成false，循环结束。在

编辑：为了避免它，您可以这样做。在

^{pr2}$