列表、循环、普通 Python答案

【问题标题】：Lists, Loops, Average Python列表、循环、普通 Python
【发布时间】：2014-11-22 17:45:03
【问题描述】：

我的代码目前有问题。该程序工作正常，但由于某种原因，当我输入所有正数时，我收到最后一个函数的错误。最后一个函数是从列表中删除所有负数。

i=0
numList = []
x = int(input("Please enter number from -9999 to end:"))
while x > -9999:
    i = i + 1
    numList.insert(i,x)
    x = int(input("Please enter number from -9999 to end:"))
    if x == -9999:
    print("The list of numbers entered:",(numList))

newList = numList[:]
secList = numList[:]

def posNumAvg(newList):
    for e in newList[:]:
        if e < 0:
            newList.remove(e)            


def negNumAvg(secList):
    for y in secList[:]:
        if y > 0:
            secList.remove(y)            

posNumAvg(newList)
negNumAvg(secList)
mydict = {'AvgPositive':(sum(newList)//len(newList)),'AvgNonPos':     (sum(secList)//len(secList)),'AvgAllNum':(sum(numList)//len(numList))}
print("The dictionary with averages is:",mydict)

【问题讨论】：

你遇到了什么错误？
那么程序不能正常工作:)

标签： python list loops python-3.x dictionary

【解决方案1】：

您正在尝试计算未定义的空列表的平均值（具体而言，列表的长度为零，因此您最终会被零除）。

你需要决定在这种情况下你想做什么并具体处理它。

顺便说一句，你可以重写

for e in newList[:]:
    if e < 0:
        newList.remove(e)

作为

newList = [e for e in newList if e >= 0]

【讨论】：

【解决方案2】：

注意：迭代列表时切勿修改列表。让我对您的代码进行一些更改

numList = []
while True: 
    x = int(input("Please enter number from -9999 to end:")
    if x == -9999:   
        print("The list of numbers entered:",(numList))
        break
    # you don't need i here, used append to insert element at last of list
    # insert is used to insert a element at specific position
    numList.append(x)

def posNumAvg(gotList):
    list_negative = []   # will contain negative number
    for e in gotList:
        if e < 0:
            list_negative.append(e)
    return list_negative

def negNumAvg(gotList):
    list_positive = []   # will contain positive number
    for y in gotList:
        if y >= 0:
            list_positive.append(y)            
    return list_positive

list_positive = posNumAvg(numList)
list_negative = negNumAvg(numList)
mydict = {'AvgPositive':(sum(list_positive)//len(list_positive)),'AvgNonPos':     (sum(list_negative)//len(list_negative)),'AvgAllNum':(sum(numList)//len(numList))}
print("The dictionary with averages is:",mydict)

您可以从一个函数中获取正数和负数：请参阅此代码

def neg_poss(gotList):
    list_positive = []   # will contain positive number
    list_negative = []   # will contain negative number
    for y in gotList:
        if y >= 0:
            list_positive.append(y)            
        else:list_negative.append(y)
    return list_positive,list_negative

list_positive,list_negative = neg_post(numList)

【讨论】：