Tuple of Pairs from List of Integers

Question

I am trying to create a list of tuple pairs from a list of integers. The list of tuple pairs will contain pairs of numbers found in the list. Example below:

listofint = [4, 3, 1, 2, 3, 1, 1, 3, 5, 1, 2, 2]
listoftuplepairs = [(3,3),(1,1),(2,2),(1,1)]

I am confused how I can implement this using a list comprehension. I have tried this below but it only returned an empty string.

listoftuplepairs = [(i,listofint.remove(i)) for i in listofint if listofint.remove(i) == i]

I understand using remove() on a list does not return anything. I have experimented with pop() but I can only pass to it a list index as the argument, instead of the actual value I want to pop() and store in my list of tuples.

Is there any other way to do this via list comprehension?

Answer 1

You can try this using Counter

Counter is used to count the number of occurrences of hashable objects.

from collections import Counter
l=[4, 3, 1, 2, 3, 1, 1, 3, 5, 1, 2, 2]
c=Counter(l)
# Counter({4: 1, 3: 3, 1: 4, 2: 3, 5: 1})

[(k,k) for k,v in c.items() for _ in range(v//2)]
# [(3, 3), (1, 1), (1, 1), (2, 2)]

So, here key k would be the number and value v would be the number of times it occurred in the list. Since you wanted pairs to get the number of pairs I did v//2 . The above approach in one-line list comprehension would be

[(k,k) for k,v in Counter(l).items() for _ in range(v//2)]

Using dict.fromkeys . Just mimicking what Counter does here.

c=dict.fromkeys(l,0)
for k in l:
    c[k]+=1

[(k,k) for k,v in c.items() for _ in range(v//2)]