在Python中如何找到列表的中值?列表可以是任意大小的，并且数字不保证是任何特定的顺序。
如果列表包含偶数个元素，则函数应返回中间两个元素的平均值。
以下是一些例子(为了便于展示，进行了排序):
median([1]) == 1
median([1, 1]) == 1
median([1, 1, 2, 4]) == 1.5
median([0, 2, 5, 6, 8, 9, 9]) == 6
median([0, 0, 0, 0, 4, 4, 6, 8]) == 2
当前回答
sorted()函数对此非常有用。使用排序函数 要对列表排序，只需返回中间值(或两个中间值的平均值) 如果列表包含偶数个元素，则为。
def median(lst):
sortedLst = sorted(lst)
lstLen = len(lst)
index = (lstLen - 1) // 2
if (lstLen % 2):
return sortedLst[index]
else:
return (sortedLst[index] + sortedLst[index + 1])/2.0
其他回答
实现它:
def median(numbers):
"""
Calculate median of a list numbers.
:param numbers: the numbers to be calculated.
:return: median value of numbers.
>>> median([1, 3, 3, 6, 7, 8, 9])
6
>>> median([1, 2, 3, 4, 5, 6, 8, 9])
4.5
>>> import statistics
>>> import random
>>> numbers = random.sample(range(-50, 50), k=100)
>>> statistics.median(numbers) == median(numbers)
True
"""
numbers = sorted(numbers)
mid_index = len(numbers) // 2
return (
(numbers[mid_index] + numbers[mid_index - 1]) / 2 if mid_index % 2 == 0
else numbers[mid_index]
)
if __name__ == "__main__":
from doctest import testmod
testmod()
来源
我为一组数字定义了一个中值函数
def median(numbers):
return (sorted(numbers)[int(round((len(numbers) - 1) / 2.0))] + sorted(numbers)[int(round((len(numbers) - 1) // 2.0))]) / 2.0
sorted()函数对此非常有用。使用排序函数 要对列表排序，只需返回中间值(或两个中间值的平均值) 如果列表包含偶数个元素，则为。
def median(lst):
sortedLst = sorted(lst)
lstLen = len(lst)
index = (lstLen - 1) // 2
if (lstLen % 2):
return sortedLst[index]
else:
return (sortedLst[index] + sortedLst[index + 1])/2.0
只要两行就够了。
def get_median(arr):
'''
Calculate the median of a sequence.
:param arr: list
:return: int or float
'''
arr = sorted(arr)
return arr[len(arr)//2] if len(arr) % 2 else (arr[len(arr)//2] + arr[len(arr)//2-1])/2
下面是不使用中值函数就能找到中值的乏味方法:
def median(*arg):
order(arg)
numArg = len(arg)
half = int(numArg/2)
if numArg/2 ==half:
print((arg[half-1]+arg[half])/2)
else:
print(int(arg[half]))
def order(tup):
ordered = [tup[i] for i in range(len(tup))]
test(ordered)
while(test(ordered)):
test(ordered)
print(ordered)
def test(ordered):
whileloop = 0
for i in range(len(ordered)-1):
print(i)
if (ordered[i]>ordered[i+1]):
print(str(ordered[i]) + ' is greater than ' + str(ordered[i+1]))
original = ordered[i+1]
ordered[i+1]=ordered[i]
ordered[i]=original
whileloop = 1 #run the loop again if you had to switch values
return whileloop
