python - 如何使用 Python 中的函数返回列表算术运算的结果

Question

这个问题已经有答案了:

error :list indices must be integers, not float for median (2 个回答)

已关闭 4 年前。

我正在尝试计算整数列表的平均值、中位数和众数。但是，我收到的错误(根据我的理解)表明我无法返回浮点答案。我不明白为什么列表会出现这种情况。我所做的只是对平均值和中位数进行基本算术运算(使用众数统计框架)。输出应该只有 1 个答案。

这是我的代码:

from statistics import mode

listOfNumbers = [1, 2, 6, 7, 8, 9, 3, 4, 5, 10, 10]
listOfNumbers.sort()
length = len(listOfNumbers)

def median(numbers):
  if((len(list)) % 2 == 0):
    median = (listOfNumbers[(length)/2] + listOfNumbers[(length)/2-1]) / 2
  else:
    median = listOfNumbers[(length-1)/2]
  return

def meanMedianMode(numbers):
    # TODO your code here!
    meanOfNumbers = (sum(numbers))/(len(numbers))
    medianOfNumbers = median(numbers)
    modeOfNumbers = mode(numbers)
    print("The mean of the numbers is: " + str(meanOfNumbers))
    print("The median of the numbers is: " + str(medianOfNumbers))
    print("The mode of the numbers is: " + str(modeOfNumbers))

meanMedianMode(listOfNumbers)

这是我的输出:

TypeError                                 Traceback (most recent call last)
<ipython-input-27-03d94981e27d> in <module>()
     21     print("The mode of the numbers is: " + str(modeOfNumbers))
     22 
---> 23 meanMedianMode(listOfNumbers)
     24 

<ipython-input-27-03d94981e27d> in meanMedianMode(numbers)
     15     # TODO your code here!
     16     meanOfNumbers = (sum(numbers))/(len(numbers))
---> 17     medianOfNumbers = median(numbers)
     18     modeOfNumbers = mode(numbers)
     19     print("The mean of the numbers is: " + str(meanOfNumbers))

<ipython-input-27-03d94981e27d> in median(numbers)
      9     median = (listOfNumbers[(length)/2] + listOfNumbers[(length)/2-1]) / 2
     10   else:
---> 11     median = listOfNumbers[(length-1)/2]
     12   return
     13 

TypeError: list indices must be integers or slices, not float

Answer 1

问题出在这一行:

median = listOfNumbers[(length-1)/2]

在 python 3 中，(length-1)/2 是一个 float，而不是 int，因此错误 list索引必须是整数或切片，而不是 float

最简单的解决方法是将结果转换回 int:

...
median = listOfNumbers[int((length - 1) / 2)]
...

事实上，我会像这样重构整个 median() 函数，因为您混合了本地变量和全局变量，并且不返回任何内容:

def median(numbers):
    length = len(numbers)
    if length % 2 == 0:
        return (listOfNumbers[int(length / 2)] + listOfNumbers[int(length / 2) - 1]) / 2
    else:
        return listOfNumbers[int((length - 1) / 2)]