我如何在Python中找到名单的中位数？

要找到列表的中位数，首先需对列表进行排序，然后根据元素数量奇偶性计算中位数。1. 对列表进行排序，可使用sorted()或.sort()方法；2. 若元素个数为奇数，中位数为中间元素，若为偶数，则为两个中间元素的平均值；3. 可使用statistics模块中的median()函数简化操作，该函数自动处理排序及奇偶情况，并在列表为空时抛出错误，因此需提前检查列表是否为空。

To find the median of a list in Python, you basically need to sort the list and then find the middle value. If there's an odd number of elements, it’s straightforward — just pick the center one. If even, average the two middle numbers.

Sort the List First

Before calculating the median, always start by sorting the list. This is crucial because the median depends on the order of values. You can use either sorted() (which returns a new sorted list) or .sort() (which modifies the original list in place).

For example:

data = [3, 1, 4, 2]
sorted_data = sorted(data)

If you're okay with changing the original list, you can do:

data.sort()

Either way works — just make sure the list is sorted before moving on.

Handle Odd and Even Lengths Differently

The next step depends on whether the number of elements is odd or even. Here's how to handle each case:

• Odd number of elements: Take the middle item directly.
• Even number of elements: Average the two middle items.

You can check the length and calculate the midpoint(s) like this:

n = len(sorted_data)
mid = n // 2

Then use a conditional to decide which calculation to perform:

• If n % 2 == 1, the median is sorted_data[mid]
• If n % 2 == 0, the median is (sorted_data[mid - 1] sorted_data[mid]) / 2

This covers both scenarios accurately.

Use the statistics Module for Simplicity

If you don’t want to write the logic from scratch, Python’s built-in statistics module has a median() function that does all this for you:

import statistics

data = [5, 1, 3]
print(statistics.median(data))  # Output: 3

It handles:

• Sorting automatically
• Both even and odd cases
• Edge cases like empty lists (raises an error)

Just be aware that if your list is empty, it will throw a StatisticsError, so you might want to add a length check beforehand if needed.

That’s basically it — whether you go with writing the logic yourself or using the built-in function, finding the median in Python isn't too bad once you know how.

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