172 lines
3.4 KiB
Markdown
172 lines
3.4 KiB
Markdown
# Set (ensemble)
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Un set est une collection **non ordonnée** et **non indexée**. On ne peut pas modifier un item, mais on peut en ajouter.
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##### Créer un set:
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set
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{'alpha', 'beta', 'gamma'}
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>>> type(un_set)
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<class 'set'>
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```
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```python
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>>> autre_set = {"alpha", "beta", "gamma", "beta", "alpha"}
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>>> len(autre_set)
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3
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>>> autre_set
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{'beta', 'alpha', 'gamma'}
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```
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```python
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# Constructor set()
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>>> un_set = set(("alpha", "beta", "gamma"))
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>>> un_set
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{'gamma', 'alpha', 'beta'}
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```
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##### Ajouter un item:
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set.add("delta")
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>>> un_set
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{'gamma', 'alpha', 'beta', 'delta'}
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```
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##### Ajouter plusieurs items:
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set.update(["delta","zeta","epsilon"])
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>>> un_set
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{'zeta', 'alpha', 'beta', 'delta', 'gamma', 'epsilon'}
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```
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##### Longueur d'un set:
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> print(len(un_set))
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3
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```
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##### Supprimer un item (remove):
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set.remove("beta")
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>>> un_set
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{'gamma', 'alpha'}
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# Si on retire un élément qui n'existe pas => Erreur
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>>> un_set.remove("delta")
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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KeyError: 'delta'
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```
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##### Supprimer un item (discard):
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set.discard("beta")
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>>> un_set
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{'gamma', 'alpha'}
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# Si on retire un élément qui n'existe pas.
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set.discard("delta")
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>>> un_set
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{'alpha', 'gamma', 'beta'}
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```
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##### Vider un set:
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set.clear()
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>>> un_set
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set()
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```
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##### Supprimer un set:
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```python
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>>> del un_set
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>>> un_set
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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NameError: name 'un_set' is not defined
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```
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##### Boucle:
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```python
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un_set = {"alpha", "beta", "gamma"}
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for x in un_set:
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print(x)
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alpha
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beta
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gamma
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```
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##### Test si un item est présent dans le set:
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```python
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un_set = {"alpha", "beta", "gamma"}
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print("alpha" in un_set)
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True
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```
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##### Set => pas d'indice:
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```python
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>>> un_set = {"alpha", "beta", "gamma"}
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>>> un_set[0]
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Traceback (most recent call last):
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File "<stdin>", line 1, in <module>
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TypeError: 'set' object does not support indexing
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```
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##### Opérateurs:
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- `a | b` (union),
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- `a & b` (intersection),
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- `a - b` (différence),
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- `a ^ b` (différence symétrique)
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#### Méthodes:
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| Méthodes | Description |
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| ----------------------------- | ----------- |
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| add() | |
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| clear() | |
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| copy() | |
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| difference() | |
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| difference_update() | |
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| discard() | |
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| intersection() | |
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| intersection_update() | |
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| isdisjoint() | |
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| issubset() | |
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| issuperset() | |
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| pop() | |
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| remove() | |
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| symmetric_difference() | |
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| symmetric_difference_update() | |
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| union() | |
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| update() | |
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