How to improve a for loop that will go through the values in my

I am writing a for loop that will go through the values in my_dictionary as well as the values in the list. If a word from the list "words" is in the my_dictionary then append the list of values where the word was found once. The code below ran the code but the list look larger than I expected.

my_dictionary = {1: ['apple','dog','cat','bird'],
                 2: ['mouse','rat','elephant','donkey'],
                 3: ['tiger','lion','bear','tortoise']}

words = ['apple', 'dog', 'mouse', 'bear','tortoise']
                
def cen_lst(my_dict, words):
    new_lst = []
    for key, value in my_dict.items():
        for word in words:
            if word in value:
                new_lst.append(value)
    return new_lst

output I expected:

['apple','dog','cat','bird', 'mouse','rat','elephant','donkey', 'tiger','lion','bear','tortoise' ]

Instead the output I am getting is:

[['apple', 'dog', 'cat', 'bird'],
 ['apple', 'dog', 'cat', 'bird'],
 ['mouse', 'rat', 'elephant', 'donkey'],
 ['tiger', 'lion', 'bear', 'tortoise'],
 ['tiger', 'lion', 'bear', 'tortoise']]

CodePudding user response：

Every time it found a matching word it appends the entire list because of this line:

    new_lst.append(value)

The value for each iteration was the entire list at that key. That's why you got a list of lists. Simply replace value with word. This causes it to just append the matching word, not the list that the word is inside.

    new_list.append(word)

CodePudding user response：

According to your description, you should use list.extend instead of list.append (you can refer to this for their differences), and do not extend every time the retrieval is successful:

>>> def cen_lst(my_dict, words):
...     new_lst = []
...     for value in my_dict.values():
...         if any(word in value for word in words):
...             new_lst.extend(value)
...     return new_lst
...
>>> cen_lst(my_dictionary, words)
['apple',
 'dog',
 'cat',
 'bird',
 'mouse',
 'rat',
 'elephant',
 'donkey',
 'tiger',
 'lion',
 'bear',
 'tortoise']