Removing duplicates from list all together in Python

Question

So I was working on a problem in which, given a list of tuples, I had to return a new list only containing the elements in which the first element of the tuple isn't duplicated. I had no problem removing duplicates but my problem is removing the original element as soon as a duplicate is found. eg.

inputList = [("test0", 20), ("test1", 25), ("test0", 30)]

This should return

[("test1", 25)]

I have after my troubles gotten it to work, however I fear my code is bad and that there is a much easier way to perform what I have done. I've done it by first removing duplicates

visited = set()
marked = []
output = []
for key, value in resList:
    if not key in visited:
        visited.add(key)
        output.append((key, value))
    else:
        marked.append(key)

I then check my new output list against my marked list

resList = []
for mark in marked:
    for i in range(len(output)):
        if mark != output[i][0]
            resList.append(output[i])

Sahith Kurapati · Accepted Answer · 2020-06-08 15:34:45Z

1

You can do it simply using list comprehension like so:

list1 = [x[0] for x in inputList]

outputList = [(x, y) for x, y in inputList if list1.count(x) == 1]

Hope it helps :)

edited Jun 8, 2020 at 15:34

answered Jun 8, 2020 at 15:24

Sahith Kurapati

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Comments

Eeshaan · Accepted Answer · 2020-06-08 15:20:28Z

0

First count how many times the first element appears in the list. For this purpose we use a dictionary d. Then use a simple list comprehension.

d = dict()
for x, y in inputList:
  d[x] = d.get(x, 0) + 1
outputList = [(x, y) for x, y in inputList if d[x] == 1]

answered Jun 8, 2020 at 15:20

Eeshaan

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wjandrea · Accepted Answer · 2020-06-08 15:30:21Z

0

Use a Counter to count occurrences in inputList, then filter out any items that occur more than once.

from collections import Counter

count = Counter(t[0] for t in inputList)
result = [t for t in inputList if count[t[0]] == 1]

print(result)  # -> [('test1', 25)]

answered Jun 8, 2020 at 15:30

wjandrea

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Jona · Accepted Answer · 2020-06-08 15:41:56Z

0

Add it to the output if it is not yet there. If it's already there, remove it and blacklist it (to avoid adding it again).

inputList = [("test0", 20), ("test1", 25), ("test0", 30)]

removed = set()
output = []
for key, value in inputList:
    keyfound = False
    for refkey, refvalue in output:
        if key == refkey:
            keyfound = True
            removed.add(key)
            output.remove((refkey, refvalue))
    if keyfound == False and key not in removed:
        output.append((key, value))

print(output)

answered Jun 8, 2020 at 15:41

Jona

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