Python remove list with duplicated fields in a list of lists

Question

I want to be able to remove an element from a list of list when a field in a list is duplicated in python3.

I.E:

Remove from the following list of lists when the second field is duplicated. From

[["John","France"], ["Mike", "France"], ["Ana","Italy"]]

To

[["John","France"], ["Ana","Italy"]]

Edit: I have tried the following loop, but I am looking forward to a more efficient way if it exists.

for element in consult_array:
    for other_elements in consult_array:
        if element[1] == other_elements[1]:
            if element != other_elements:
                consult_array.pop(element)

Did you try using one or more `for` loops and `if` statements? — mkrieger1, Mar 04 '20 at 14:46
add each country to a dict everytime a new one found and then, if a country is on the dict pop it out of the list? — Rauññ, Mar 04 '20 at 14:47
Yes @mkrieger1, I will edit my answer with the code. I was looking for a more efficient way (if it exists) — Dani Gonzalez, Mar 04 '20 at 14:56

score 2 · Accepted Answer · answered Mar 04 '20 at 14:51

2

data = [["John", "France"], ["Mike", "France"], ["Ana", "Italy"]]

output = []
already_seen_countries = set()

for item in data:
    country = item[1]
    if country not in already_seen_countries:
        output.append(item)
        already_seen_countries.add(country)

print(output)  # [['John', 'France'], ['Ana', 'Italy']]

answered Mar 04 '20 at 14:51

Michael H.

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If anyone is facing this problem in the future: To remove it from the original list, I put this code in a function with the list as arg, and I am returning the output and assinging it to the original list. – Dani Gonzalez Mar 04 '20 at 15:16

kederrac · Answer 2 · 2020-03-04T16:59:44.450

0

if you like one line solutions:

l = [["John","France"], ["Mike", "France"], ["Ana","Italy"]]
list(t for t in {e[1]: e for e in l[::-1]}.values())[::-1]

output:

[['John', 'France'], ['Ana', 'Italy']]

edited Mar 04 '20 at 16:59

answered Mar 04 '20 at 14:58

kederrac

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Can you explain the significance of `[::-1]`? – mkrieger1 Mar 04 '20 at 15:04
this does not "remove" the items, it creates a new list – Pablo Tato Ramos Mar 04 '20 at 15:06
@mkrieger1 to [reverse a list](https://stackoverflow.com/questions/3940128/how-can-i-reverse-a-list-in-python) – kederrac Mar 04 '20 at 15:06
I know, but why is it necessary here? – mkrieger1 Mar 04 '20 at 15:07
@PabloTatoRamos the end result is the same, where is the problem? – kederrac Mar 04 '20 at 15:07

Python remove list with duplicated fields in a list of lists

2 Answers2