检查列表列表是否具有相同大小的列表

Question

我需要验证我的列表列表在 python 中是否具有相同大小的列表

myList1 = [ [1,1] , [1,1]] // This should pass. It has two lists.. both of length 2
myList2 = [ [1,1,1] , [1,1,1], [1,1,1]] // This should pass, It has three lists.. all of length 3
myList3 = [ [1,1] , [1,1], [1,1]] // This should pass, It has three lists.. all of length 2
myList4 = [ [1,1,] , [1,1,1], [1,1,1]] // This should FAIL. It has three list.. one of which is different that the other 

我可以编写一个循环来迭代列表并检查每个子列表的大小。有没有更Pythonic的方法来实现结果。

Answer 1

all(len(i) == len(myList[0]) for i in myList)

为了避免每个项目产生 len(myList[0]) 的开销，您可以将其存储在变量中

len_first = len(myList[0]) if myList else None
all(len(i) == len_first for i in myList)

如果您也想了解为什么它们并不完全相同

from itertools import groupby
groupby(sorted(myList, key=len), key=len)

将按长度对列表进行分组，以便您可以轻松地看到奇怪的列表

Answer 2

你可以尝试：

test = lambda x: len(set(map(len, x))) == 1

test(myList1) # True
test(myList4) # False

基本上，您可以获得每个列表的长度并根据这些长度创建一个集合，如果它包含单个元素，则每个列表具有相同的长度

Answer 3

def equalSizes(*args):
    """
    # This should pass. It has two lists.. both of length 2
    >>> equalSizes([1,1] , [1,1])
    True

    # This should pass, It has three lists.. all of length 3
    >>> equalSizes([1,1,1] , [1,1,1], [1,1,1])
    True

    # This should pass, It has three lists.. all of length 2
    >>> equalSizes([1,1] , [1,1], [1,1])
    True

    # This should FAIL. It has three list.. one of which is different that the other
    >>> equalSizes([1,1,] , [1,1,1], [1,1,1])
    False
    """
    len0 = len(args[0])
    return all(len(x) == len0 for x in args[1:])

要测试它，请将其保存到文件中

so.py

并像这样运行它：

$ python -m doctest so.py -v
Trying:
    equalSizes([1,1] , [1,1])
Expecting:
    True
ok
Trying:
    equalSizes([1,1,1] , [1,1,1], [1,1,1])
Expecting:
    True
ok
Trying:
    equalSizes([1,1] , [1,1], [1,1])
Expecting:
    True
ok
Trying:
    equalSizes([1,1,] , [1,1,1], [1,1,1])
Expecting:
    False
ok

Answer 4

如果您想在失败案例中获得更多数据，您可以这样做：

myList1 = [ [1,1] , [1,1]]
lens = set(itertools.imap(len, myList1))
return len(lens) == 1
# if you have lists of varying length, at least you can get stats about what the different lengths are

Answer 5

作为一名计算数学家，我建议使用

variance

长度。零方差意味着所有值都相等。

import statistics

def check_same_lengh(iterables):
    variation = statistics.variance(len(iterable) for iterable in iterables)

    if variation != 0:
        raise ValueError('Their lengths are not the same.')


iterables = [[1, 1, 1], [2, 2, 2], [3, 3, 3]]
check_same_lengh(iterables)