48 lines
1.3 KiB
Markdown
48 lines
1.3 KiB
Markdown
---
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title: Learn About Python Sets
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---
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`Set`s in Python are a type of mutable but unordered data structure, which can only contain *unique* elements. In other words, it is equivalent to sets in math.
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**Creation:**
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`set` literal:
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Curly brackets, `{}`, *cannot* be used to create an empty set:
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```python
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>>> not_set = {} # set constructor must be used to make empty sets.
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>>> type(not_set) # Empty curly brackets create empty dictionaries.
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<class 'dict'>
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```
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You can only create an empty set by using the `set()` method.
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```python
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>>> example_set = set()
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>>> type(example_set)
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<class 'set'>
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```
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However, if elements are included within the curly brackets, then it would be acceptable syntax to create a set.
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```python
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>>> example_set_2 = {1, 2, 3}
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>>> type(example_set_2)
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<class 'set'>
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````
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## Converting Iterable to Set
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If `set(...)` contains an iterable such as a list, a string, or a tuple as an element, it will return a set containing its' elements. This will remove all duplicate values from the list.
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```python
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>>> example_set_3 = set('some string')
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>>> example_set_3
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{' ', 't', 'g', 'o', 'r', 'i', 's', 'e', 'n', 'm'}
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```
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If you want to convert an iterable like a list to a set, you can do that by passing it to the `set()` function.
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```python
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>>> a = [11,2,2,6,6,4,8,9,9,7]
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>>> a = set(a)
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>>> print(a) # {2, 4, 6, 7, 8, 9, 11}
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```
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