September 23, 2021    /    Viewed: 316    /    Comments: 0    /    Edit

Examples of how to get unique values in a list in python:

### Create a list in python

Let's first create a list with unique values:

````mylist1 = ['a', 'b', 'c', 'd']`
```

and then create another bigger list using those unique values:

````import random`

`mylist2 = [random.choice(mylist1) for i in range(20)]`

`mylist2`
```

gives for example:

````['d',`
` 'c',`
` 'd',`
` 'd',`
` 'b',`
` 'd',`
` 'a',`
` 'b',`
` 'b',`
` 'd',`
` 'a',`
` 'b',`
` 'a',`
` 'b',`
` 'a',`
` 'd',`
` 'b',`
` 'd',`
` 'a',`
` 'b']`
```

Goal: get unique values from mylist2.

### Get unique values in a list

There are several solutions to do that.

### Convert the list into a set

A straightforward solution is to convert the list into a set (see Data Structures):

````mylist2 = set(mylist2)`
```

and to convert again into a list

````mylist2 = list(mylist2)`

`print(mylist2)`
```

gives

````['d', 'a', 'b', 'c']`
```

Note: to sort the list:

````mylist2.sort()`

`print(mylist2)`
```

gives then

````['a', 'b', 'c', 'd']`
```

### Convert the list into a matrix

Another solution is to convert into a matrix

````import numpy as np`

`mylist2 = np.array(mylist2)`
```

since numpy as the function unique()

````mylist2 = np.unique(mylist2)`
```

and convert again into a list

````mylist2 = list(mylist2)`

`mylist2`
```

gives

````['a', 'b', 'c', 'd']`
```

### Iterate over each value with a for loop

Another solution is to simply iterate over each value with a for loop

````mylist3 = []`

`for i in mylist2:`
`        if i not in mylist3:`
`                mylist3.append(i)`

`mylist2 = mylist3`

`mylist2.sort()`

`print(mylist2)`
```

gives

````['a', 'b', 'c', 'd']`
```  ##### Daidalos

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