Python - 列表列表与近似浮点数的比较

Question

我对编程有点陌生，我想比较python中的两个列表列表，而这些列表中的浮点数可能有错误。这里有一个例子：

first_list = [['ATOM', 'N', 'SER', -1.081, -16.465,  17.224], 
              ['ATOM', 'C', 'SER', 2.805, -3.504,  6.222], 
              ['ATOM', 'O', 'SER', -17.749, 16.241,  -1.333]]
secnd_list = [['ATOM', 'N', 'SER', -1.082, -16.465,  17.227],
              ['ATOM', 'C', 'SER', 2.142, -3.914,  6.222], 
              ['ATOM', 'O', 'SER', -17.541, -16.241,  -1.334]]

预期输出：

Differences = ['ATOM', 'C', 'SER', 2.805, -3.504,  6.222]

到目前为止，我的尝试：

def aprox (x, y):
    if x == float and y == float:
        delta = 0.2 >= abs(x - y)
        return delta
    else: rest = x, y
    return rest
def compare (data1, data2):
    diff = [x for x,y in first_list if x not in secnd_list and aprox(x,y)] + [x for x,y in secnd_list if x not in first_list and aprox(x,y)]
    return diff

或者在元组的帮助下，但我不知道如何构建近似值：

def compare (data1, data2):
    first_set = set(map(tuple, data1))
    secnd_set = set(map(tuple, data2))
    diff = first_set.symmetric_difference(secnd_set)
    return diff

希望你能帮助我！ :)

Answer 1

行

if x == float and y == float

不准确...检查变量类型的正确方法是使用 type() 函数...尝试将上面的行替换为

if type(x) is float and type(y) is float:

Answer 2

这有点笨拙，但我在飞行中做到了，它应该能给你带来想要的结果。正如我在代码中提到的，您将阈值设置为 0.2这意味着应该返回两行，而不是您提到的一行。

def discrepancies(x, y):
    for _, (row1, row2) in enumerate(zip(x, y)):
        for _, (item1, item2) in enumerate(zip(row1[3:],row2[3:])):
            if abs(item1 - item2) >= 0.2:
                print row1
                break
discrepancies(first_list, secnd_list)
['ATOM', 'C', 'SER', 2.805, -3.504, 6.222]
['ATOM', 'O', 'SER', -17.749, 16.241, -1.333]

有几个警告，随着每个 for 循环添加 O(n( 并且对于列表中较大的列表，我会使用我认为它被调用的 itertools.izip 函数，这会变得相当慢。希望这有帮助！

Answer 3

也许您可以遍历两者中的每个元素，然后比较子元素：然后，当任何子元素不相等时，可以根据其类型将其添加到结果中，即如果两个字符串不相等，可以将其添加到结果中，或者如果它是浮点数并且math.isclose()可用于近似：

注意：进行了更正以匹配预期的输出，first_list的第三个元素中缺少负号

import math
first_list = [['ATOM', 'N', 'SER', -1.081, -16.465,  17.224], 
              ['ATOM', 'C', 'SER', 2.805, -3.504,  6.222], 
              ['ATOM', 'O', 'SER', -17.749, -16.241,  -1.333]] # changes made
secnd_list = [['ATOM', 'N', 'SER', -1.082, -16.465,  17.227],
              ['ATOM', 'C', 'SER', 2.142, -3.914,  6.222], 
              ['ATOM', 'O', 'SER', -17.541, -16.241,  -1.334]]
diff = []
for e1, e2 in zip(first_list, secnd_list):
    for e_sub1, e_sub2 in zip(e1, e2):
        # if sub-elements are not equal
        if e_sub1 != e_sub2:
            # if it is string and not equal
            if isinstance(e_sub1, str):
                diff.append(e1)
                break # one element not equal so no need to iterate other sub-elements
            else:  # is float and not equal
                # Comparison made to 0.2
                if not math.isclose(e_sub1, e_sub2, rel_tol=2e-1):
                    diff.append(e1)
                    break # one element not equal so no need to iterate other sub-elements
diff

输出：

[['ATOM', 'C', 'SER', 2.805, -3.504, 6.222]]