ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() - followed by a TypeError

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I want to check if a dictionary already exists in a group of lists. Without the use of any() in the if-statement, I received the following error:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

But then when I do make use of the any(), the following error arises:

TypeError: 'bool' object is not iterable

I don't know where I'm going wrong. Any help or guidance on this would be much appreciated.

import numpy as np

compile = []
MY_LIST = [[['Mon'], np.array([4,2,1,3]), ['text'], ['more_text', 0.1]], [['Mon'], np.array([4,2,1,3]), ['text'], ['more_text', 0.1]], [['Tues'], np.array([3, 1, 2, 4]), ['text2'], ['more_text2', 0.2]]]
for group in MY_LIST:
    my_dict = {'A': group[0], 'B': group[1], 'C': group[2],
               'D': group[3]}

    if any(my_dict not in compile):  # Error here
        compile.append(my_dict)
    print (compile)

The expected output should be:

[{'A': ['Mon'], 'B': array([4, 2, 1, 3]), 'C': ['text'], 'D': ['more_text', 0.1]}, {'A': ['Tues'], 'B': array([3, 1, 2, 4]), 'C': ['text2'], 'D': ['more_text2', 0.2]}]
boolean-logic list python
1 Answers

The issue boils down to the fact that you can't directly compare two numpy arrays using == alone, unlike most types. You need to define a custom function to compare two values in the dictionaries to handle the different types:

import numpy as np

def compare_element(elem1, elem2):
    if type(elem1) != type(elem2):
        return False
    if isinstance(elem1, np.ndarray):
        return (elem1 == elem2).all()
    else:
        return elem1 == elem2

result = []
MY_LIST = [
    [['Mon'], np.array([4,2,1,3]), ['text'], ['more_text', 0.1]],
    [['Mon'], np.array([4,2,1,3]), ['text'], ['more_text', 0.1]],
    [['Tues'], np.array([3, 1, 2, 4]), ['text2'], ['more_text2', 0.2]]
]

for group in MY_LIST:
    elem_to_append = dict(zip(['A', 'B', 'C', 'D'], group))

    should_append = True
    for item in result:
        if all(compare_element(item[key], elem_to_append[key]) for key in item):
            should_append = False
            break

    if should_append:
        result.append(elem_to_append)

print(result)
user_177698150
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