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在 (3987) 和 (5026) 范围内 [Num] 字段中的数字的平均值是多少？

该字段在其下方是excel上的字段[4]。

**amount       code    quan val     number  Random**
2.11    I[N8U7]:75  184 Blue    2254    Potato
3.13    Z[V0L8]:64  131 Blue    6349    Carrot
4.24    B[Y1U2]:38  56  Blue    4164    Mushrooms
7.32    T[Z7N0]:67  329 Red     2079    Pear
9.1     C[T8C5]:83  344 Blue    1045    Apple
11.17   M[P4J9]:38  267 Blue    1254    Strawberry
2.21    E[S1G7]:62  446 Red     2223    Vanilla
1.41    W[M4M5]:96  8   Red     6745    Juice
2.31    W[P3E1]:24  215 Red     1223    Orange
0.12    E[M5K0]:78  424 Blue    2385    Pineapple
3.91    A[A9M2]:33  367 Red     3354    Grape
3.1     W[N2E2]:70  121 Blue    7716    Watermelon
10.21   J[H2W8]:17  253 Red     1017    Yogurt
5.1     G[K5L5]:08  216 Red     1039    Peppers
1.14    V[Z2C3]:L75 419 Blue    2520    Onions
1.02    Q[I1I2]:20  380 Red     2700    Chocolate
0.19    S[P1X2]:43  133 Blue    3171    Cheese
7.21    Z[B2E3]:46  126 Blue    2971    Ham
10.21   L[F6V1J:28  249 Red     7574    Blueberry
1.02    X[B0N3]:65  243 Blue    3441    Water

我已经尝试了以下代码，但我不知道还能做什么。提前致谢

file=open ('3114644b.csv','r')

def mylist():
    alist=[]
    for line in file:
        field = line.split(',')
        if field[0]=='bid' or field[0]=='leave':
            alist.append(float(field[4]))
    return alist

blist=mylist()
total = 0
count = 0
for num in blist:
    total +=  num
    count += 1

average = total / count

print ("the average of the values)

file.close
4

2 回答 2

4

使用csv模块，它是为这样的任务设计的：

import csv

total = count = 0

with open('3114644b.csv', newline='') as f:
    reader = csv.reader(f)
    next(reader, None)  # skip the first row of headers

    for row in reader:
        total += float(row[4])
        count += 1

if count:
    # only calculate the average if there was actually anything in the file
    average = total / count
    print('The average of the values is {}'.format(average))

上述代码还使用文件作为上下文管理器（带有with语句）；块完成后with，文件会自动为您关闭。

在您的版本中，您尝试手动关闭文件，但仅设法引用该.close()方法，而不是实际调用它。

我们也不会将所有值读入列表中，而不是当您可以将这些值相加并计算您相加的值的数量时。这使用更少的内存，并且可以快速高效地处理甚至是巨大的 CSV 文件。

对于您的示例数据，上面的代码输出：

这些值的平均值是 3261.2

于 2013-05-10T20:19:42.487 回答
0

这是一个不使用该cvs模块的版本。（请注意，鼓励您学习如何使用适合每个任务的模块）

data = []

# This next line closes the file as soon as the block ends (as Martijn suggests)
with open ('3114644b.csv','r') as f:
    for line in f:
        field = line.split(',')
        if field[0] in {'bid', 'leave'}:
            # Note that the 4th column you want to refer to is actually the list
            # list elemnt with index 3, not 4. List indexes start with 0
            data.append(float(field[3]))

# The 'sum()' function is the best choice for your problem as karthirk suggested
# The 'len()' function is a built-in function that returns the number of items
# a list has
average = sum(data)/len(data)

print ("The average of the values is %f" % average)
于 2013-05-10T20:41:43.560 回答