Sentinel Loop Python

Question

我应该如何在python中设置一个哨兵循环，只有当新输入的数字大于旧的输入数字时循环才会继续运行？

这就是我现在的情况，但我知道这是不对的。

totalScore = 0 
    loopCounter = 0 
    scoreCount = 0 
    newScore = 0 
    oldscore = newscore - 1 
    print("Enter the scores:") 
    score = (raw_input("Score 1")) 
    while newScore >= oldScore: 
     newScore = int(raw_input("Score ") + (loopCounter + 1)) 
     scoreTotal = scoreTotal+newScore+oldScore 
     scoreCount = scoreCount + 1 
     loopCounter = loopCounter + 1 
    averageScore = scoreTotal/scoreCount 
    print "The average score is " + str(averageScore) 

Answer 1

处理这种情况的事实上的方法是使用一个列表，而不是扔掉每次个人得分。

scores = [0] # a dummy entry to make the numbers line up 
print("Enter the scores: ") 
while True: # We'll use an if to kick us out of the loop, so loop forever 
    score = int(raw_input("Score {}: ".format(len(scores))) 
    if score < scores[-1]: 
     print("Exiting loop...") 
     break 
     # kicks you out of the loop if score is smaller 
     # than scores[-1] (the last entry in scores) 
    scores.append(score) 
scores.pop(0) # removes the first (dummy) entry 
average_score = sum(scores)/len(scores) 
# sum() adds together an iterable like a list, so sum(scores) is all your scores 
# together. len() gives the length of an iterable, so average is easy to test! 
print("The average score is {}".format(average_score)) 

Answer 2

你想不断要求用户输入一个新的数字，而每次输入一个更大的数字。您可以使用一个列表，以保持每一个得分进入，然后使用sum built-in function做的工作适合你：

scores = [] 
while True: 
    current_size = len(scores) 
    score = int(raw_input("Score %s" % (current_size + 1))) 
    # Check if there's any score already entered and then if the new one is 
    # smaller than the previous one. If it's the case, we break the loop 
    if current_size > 0 and score < scores[-1]: 
     break 
    scores.append(score) 

# avg = total of each scores entered divided by the size of the list 
avg = sum(scores)/len(scores) 
print "The average score is %s" % avg 

Answer 3

你的代码中有各种问题，将不能运行。这是一个工作版本，可以完成你想要的功能。

使用while循环管理旧值和新值是编码中常见的习惯用法，值得练习。

编辑：我搞砸了自己的代码行的顺序。现在的代码给出了正确的平均值。

scoreTotal = 0 
loopCounter = 0 
scoreCount = 0 
newScore = 0 
oldScore = 0 
print("Enter the scores:") 
newScore = int(raw_input("Score 1: ")) 
while newScore >= oldScore: 
    scoreTotal += newScore 
    scoreCount += 1 
    loopCounter += 1 
    oldScore = newScore 
    newScore = int(raw_input("Score " + str(loopCounter + 2) + ": ")) 
averageScore = float(scoreTotal)/float(scoreCount) 
print scoreTotal, scoreCount 
print "The average score is " + str(averageScore) 

Answer 4

继雷蒙德赫廷杰的谈话和阿米尔的博客文章http://blog.amir.rachum.com/blog/2013/11/10/python-tips-iterate-with-a-sentinel-value/

In [1]: def loop(): 
    ...:  old = 0 
    ...:  while True: 
    ...:   new = raw_input("gimme") 
    ...:   yield new > old 
    ...:   old = new 
    ...:   

In [2]: l = loop() 

In [4]: list(iter(l.next, False)) 
gimme1 
gimme2 
gimme0 
Out[4]: [True, True]