尝试从二维列表（从.txt文件读取）中查找平均更改率时，结果不正确

Question

我创建了一个程序，可以读取一个由价格列表组成的.txt文件。程序将创建一个二维列表来存储周数、价格和与前一周相比的变化。用户将输入所需的开始周和结束周。你知道吗

如果用户将“开始周”输入为“1”，将“结束周”输入为“6”： 平均变化应为“-0.30” 最高变化应为“第4周”，变化为“2.80” 最低变化应为“第5周”，变化为“-4.93”

然而，我的数字完全错了。你知道吗

这是我的密码：

# get two dimensional list
priceList = []

#open the file
priceFile = open ('MicrosoftPrices.txt', 'r')

#create variable for start year
week = 1
price = float (priceFile.readline())

#special case for week 1

#initialize loop counter
i = 0

while price != '':
    priceList.append ([0,0,0])

    priceList [i][0] = week
    priceList [i][1] = float (price)

    if week == 1:
        priceList [i][2] = 0
    else:
        priceList[i][2] = ((priceList[i][1] - priceList[i-1][1])/priceList[i-1][1])

    #read the next line
    price = priceFile.readline()

    #add to the counter
    i += 1

    #go to next week
    week = week + 1

#initialize start and end weeks
startWeek = 0
endWeek = 0

#define start week validation
def FirstValidation (startWeek):

    startWeek = -1

    while startWeek == -1:
        startWeek = input ('What week would you like to start with?')

        try:
            if startWeek == '':
                startWeek = 1
                break

            startWeek = int (startWeek)

        except Exception:
            print ('Year must be a valid integer between 1 and 52')

        else:
            if startWeek >= 1 and startWeek <= 52:
                break
            else:
                startWeek = -1
                print ('ERROR: Week must be a valid integer between 1 and 52! Please try again.')

    return startWeek

#define end week validation
def LastValidation (endWeek):
    endWeek = -1

    while endWeek == -1:
        endWeek = input ('What week would you like to end with?')

        try:
            if endWeek == '':
                endWeek = 52
                break

            endWeek = int (endWeek)

        except Exception:
            print ('Year must be a valid integer between 1 and 52')
        else:
            if endWeek >= startWeek and endWeek <= 52:
                break
            else:
                endWeek = -1
                print ('ERROR: Week must be a valid integer between 1 and 52! Please try again.')

    return endWeek

def main ():

    #call week validations
    startWeekVal = FirstValidation ('Start Week')
    endWeekVal = LastValidation ('End Week')


    #initialize min and max
    maxChange = 0
    minChange = 100
    maxIndex = 0
    minIndex = 0
    total = 0
    count = 0

    for j in range (startWeekVal, endWeekVal +1):
        if priceList [j][2] > maxChange:
            maxChange = priceList [j][2]
            maxIndex = j
        if priceList [j][2] < minChange:
            minChange = priceList [j][2]
            minIndex = j

        #calc average
        total += priceList [j][2]
        count += 1

        #compute average
        average = total / count

    print ('Start Week:', startWeekVal)
    print ('End Week:', endWeekVal)
    print ('The average change is ', average)
    print ('The week with the highest change is week' , priceList [maxIndex][0], 'with $', format (maxChange, '.2f'))
    print ('The week with the lowest change is week' , priceList [minIndex][0], 'with $', format (minChange, '.2f'))

    #close the file
    priceFile.close()

#call main
main ()

以下是.txt文件供参考：

52.33
50.99
52.29
55.09
50.16
50.50
51.82
51.30
52.03
53.07
53.49
54.21
55.57
54.42
55.65
51.78
49.87
50.39
51.08
50.62
52.32
51.79
51.48
50.13
49.83
51.16
52.30
53.70
56.57
56.68
57.96
57.94
57.62
58.03
57.67
56.21
57.25
57.43
57.60
57.80
57.42
59.66
59.87
58.71
59.02
60.35
60.53
59.25
61.97
62.30
63.24
62.14

Answer 1

我认为，这段代码应该满足您的要求：

# get two dimensional list
priceList = []

#open the file
priceFile = open ('MicrosoftPrices.txt', 'r')

#create variable for start year
week = 1
price = float (priceFile.readline())

#special case for week 1

#initialize loop counter
i = 0

while price != '':
    priceList.append ([0,0,0])

    priceList [i][0] = week
    priceList [i][1] = float (price)

    if week == 1:
        priceList [i][2] = 0
    else:
        priceList[i][2] = (priceList[i][1] - priceList[i-1][1])

    #read the next line
    price = priceFile.readline()

    #add to the counter
    i += 1

    #go to next week
    week = week + 1

#initialize start and end weeks
startWeek = 0
endWeek = 0

#define start week validation
def FirstValidation (startWeek):

    startWeek = -1

    while startWeek == -1:
        startWeek = input ('What week would you like to start with?')

        try:
            if startWeek == '':
                startWeek = 1
                break

            startWeek = int (startWeek)

        except Exception:
            print ('Year must be a valid integer between 1 and 52')

        else:
            if startWeek >= 1 and startWeek <= 52:
                break
            else:
                startWeek = -1
                print ('ERROR: Week must be a valid integer between 1 and 52! Please try again.')

    return startWeek

#define end week validation
def LastValidation (endWeek):
    endWeek = -1

    while endWeek == -1:
        endWeek = input ('What week would you like to end with?')

        try:
            if endWeek == '':
                endWeek = 52
                break

            endWeek = int (endWeek)

        except Exception:
            print ('Year must be a valid integer between 1 and 52')
        else:
            if endWeek >= startWeek and endWeek <= 52:
                break
            else:
                endWeek = -1
                print ('ERROR: Week must be a valid integer between 1 and 52! Please try again.')

    return endWeek

def main ():

    #call week validations
    startWeekVal = FirstValidation ('Start Week')
    endWeekVal = LastValidation ('End Week')


    #initialize min and max
    maxChange = 0
    minChange = 100
    maxIndex = 0
    minIndex = 0
    total = 0
    count = 0

    print priceList

    for j in range (startWeekVal-1, endWeekVal):
        if priceList [j][2] > maxChange:
            maxChange = priceList [j][2]
            maxIndex = j
        if priceList [j][2] < minChange:
            minChange = priceList [j][2]
            minIndex = j

        #calc average
        total += priceList [j][2]
        count += 1

        #compute average

    average = total / count

    print ('Start Week:', startWeekVal)
    print ('End Week:', endWeekVal)
    print ('The average change is ', average)
    print ('The week with the highest change is week' , priceList [maxIndex][0], 'with $', format (maxChange, '.2f'))
    print ('The week with the lowest change is week' , priceList [minIndex][0], 'with $', format (minChange, '.2f'))

    #close the file
    priceFile.close()

#call main
main ()

有几个问题，你迭代的范围上移了一个。也就是说，如果你试着把开始一周定为1，结束一周定为2，那么实际上应该是2和3。然后，您尝试跟踪每个子数组的第三个条目中的更改百分比，然后再次求平均值。相反，在第三个条目中跟踪震级变化，然后在最后求平均值。你知道吗

Answer 2

我推荐这样的

def stats(y, start, stop):
    maximum = max(y[start, stop])
    minimum = min(y[start, stop])
    average = sum(y[start, stop])/len(y[start, stop])
    return maximum, minimum, average

with open('prices.txt') as f:
    l = list(map(float, f.readlines()))

x = l[0]
y = []
for i in l:
    y.append(i-x)
    x=i

#We now have two lists.  l[i] has the price at week i, and 
    #y[i] has the change in price from week i-1

start_week = int(input("Start Week: ")) -1
end_week = int(input("End Week: "))

maximum, minimum, average = stats(y, start_week, end_week)

print("Maximum {}".format(maximum))
print("Minimum {}".format(minimum))
print("Average {}".format(average))