CODEWITHSUNDEEP
pythonlisttuples
Aamir Khan
Aamir Khan

Reputation: 57

List append 2 tuples reversed

I have a list like this

Test = [(3.0, 5.0), (1.0, 7.0), (3.0, 4.0)]

I want to append reversed elements in each tuple (I might be using wrong language)

Here is the example

I want to append this

(5.0, 3.0), (7.0, 1.0), (4.0, 1.0)

If possible I don't want to append duplicates in the list

I tried this

Test.append(Test[i][1]),(Test[i][0]) # (where i = 0 to 1)

but failed

Upvotes: 0

Views: 167

Answers (3)

Mayur Koshti
Mayur Koshti

Reputation: 1852

>>> Test = [(3.0, 5.0), (1.0, 7.0), (3.0, 4.0)]
>>> T = [(i[1], i[0]) for i in Test]
>>> T
[(5.0, 3.0), (7.0, 1.0), (4.0, 3.0)]

Upvotes: 0

Steven Summers
Steven Summers

Reputation: 5384

Didn't quite follow what you meant with i though. But a simple list comprehension will work

myList = [(5.0, 3.0), (7.0, 1.0), (4.0, 3.0), (3.0, 5.0)]
myList.extend([(y, x) for x, y in myList if (y, x) not in myList])

Or just use a normal for-loop. You can either append to the same list, or add items to new list and then extend. I personally prefer new list and then extend as otherwise you will end up iterating over the newly appended items (which makes no difference aside from efficiency)

myList = [(5.0, 3.0), (7.0, 1.0), (4.0, 3.0), (3.0, 4.0)]
res = []
for x, y in myList:
    if (y, x) not in myList and (y, x) not in res:
        res.append((y, x))
myList.extend(res)

#Output 
[(5.0, 3.0), (7.0, 1.0), (4.0, 3.0), (3.0, 5.0), (1.0, 7.0), (3.0, 4.0)]

Upvotes: 2

thefourtheye
thefourtheye

Reputation: 239483

To reverse the elements in the list, you can simply use reversed function, and recreate the list, like this

>>> test = [(3.0, 5.0), (1.0, 7.0), (3.0, 4.0)]
>>> [tuple(reversed(item)) for item in test]
[(5.0, 3.0), (7.0, 1.0), (4.0, 3.0)]

If possible I don't want to append duplicates in the list

As you want to remove the duplicates as well, the best option would be to use collections.OrderedDict like this

>>> from collections import OrderedDict
>>> list(OrderedDict.fromkeys(tuple(reversed(item)) for item in test).keys())
[(5.0, 3.0), (7.0, 1.0), (4.0, 3.0)]

Upvotes: 1

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