# Python | Check if list contains all unique elements

• Last Updated : 23 Dec, 2018

Some list operations require us to check if all the elements in the list are unique. This usually happens when we try to perform the set operations in a list. Hence this particular utility is essential at these times. Lets discuss certain methods by which this can be performed.

Method #1 : Naive Method
Solutions usually start from the simplest method one can apply to perform a particular task. Here you can use a nested loop to check if after that element similar element exists in the remaining list.

 `# Python3 code to demonstrate ``# to test all elements in list are unique``# using naive method `` ` `# initializing list ``test_list ``=` `[``1``, ``3``, ``4``, ``6``, ``7``]`` ` `# printing original list ``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `flag ``=` `0`` ` `# using naive method ``# to check all unique list elements``for` `i ``in` `range``(``len``(test_list)):``        ``for` `i1 ``in` `range``(``len``(test_list)):``            ``if` `i !``=` `i1:``                ``if` `test_list[i] ``=``=` `test_list[i1]:``                    ``flag ``=` `1`` ` ` ` `# printing result``if``(``not` `flag) :``    ``print` `(``"List contains all unique elements"``)``else` `: ``    ``print` `(``"List contains does not contains all unique elements"``)`

Output :

```The original list is : [1, 3, 4, 6, 7]
List contains all unique elements
```

Method #2 : Using `len() + set()`
This is most elegant way in which this problem can be solved by using just a single line. This solution converts the list to set and then tests with original list if contains similar no. of elements.

 `# Python3 code to demonstrate ``# to test all elements in list are unique``# using set() + len()`` ` `# initializing list ``test_list ``=` `[``1``, ``3``, ``4``, ``6``, ``7``]`` ` `# printing original list ``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `flag ``=` `0`` ` `# using set() + len()``# to check all unique list elements``flag ``=` `len``(``set``(test_list)) ``=``=` `len``(test_list)`` ` ` ` `# printing result``if``(flag) :``    ``print` `(``"List contains all unique elements"``)``else` `: ``    ``print` `(``"List contains does not contains all unique elements"``)`

Output :

```The original list is : [1, 3, 4, 6, 7]
List contains all unique elements
```

Method #3 : Using `Counter.itervalues()`
This is one of the different methods and uses the frequency obtained of all the elements using Counter, and checks if any of the frequency is greater than 1.

 `# Python code to demonstrate ``# to test all elements in list are unique``# using Counter.itervalues()``from` `collections ``import` `Counter`` ` `# initializing list ``test_list ``=` `[``1``, ``3``, ``4``, ``6``, ``7``]`` ` `# printing original list ``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `flag ``=` `0`` ` `# using Counter.itervalues() ``# to check all unique list elements``counter ``=` `Counter(test_list)``for` `values ``in` `counter.itervalues():``        ``if` `values > ``1``:``            ``flag ``=` `1`` ` ` ` `# printing result``if``(``not` `flag) :``    ``print` `(``"List contains all unique elements"``)``else` `: ``    ``print` `(``"List contains does not contains all unique elements"``)`

Output :

```The original list is : [1, 3, 4, 6, 7]
List contains all unique elements
```

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