Aide-mémoire complet sur les structures de données Python

Aide-mémoire complet sur les structures de données Python

Table des matières

1. Listes
2. Tuples
3. Ensembles
4. Dictionnaires
5. Cordes
6. Tableaux
7. Piles
8. Files d'attente
9. Listes liées
10. Arbres
11. Des tas
12. Graphiques
13. Structures de données avancées

Listes

Les listes sont des séquences ordonnées et mutables.

Création

empty_list = []
list_with_items = [1, 2, 3]
list_from_iterable = list("abc")
list_comprehension = [x for x in range(10) if x % 2 == 0]

Opérations communes

# Accessing elements
first_item = my_list[0]
last_item = my_list[-1]

# Slicing
subset = my_list[1:4]  # Elements 1 to 3
reversed_list = my_list[::-1]

# Adding elements
my_list.append(4)  # Add to end
my_list.insert(0, 0)  # Insert at specific index
my_list.extend([5, 6, 7])  # Add multiple elements

# Removing elements
removed_item = my_list.pop()  # Remove and return last item
my_list.remove(3)  # Remove first occurrence of 3
del my_list[0]  # Remove item at index 0

# Other operations
length = len(my_list)
index = my_list.index(4)  # Find index of first occurrence of 4
count = my_list.count(2)  # Count occurrences of 2
my_list.sort()  # Sort in place
sorted_list = sorted(my_list)  # Return new sorted list
my_list.reverse()  # Reverse in place

Techniques avancées

# List as stack
stack = [1, 2, 3]
stack.append(4)  # Push
top_item = stack.pop()  # Pop

# List as queue (not efficient, use collections.deque instead)
queue = [1, 2, 3]
queue.append(4)  # Enqueue
first_item = queue.pop(0)  # Dequeue

# Nested lists
matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
flattened = [item for sublist in matrix for item in sublist]

# List multiplication
repeated_list = [0] * 5  # [0, 0, 0, 0, 0]

# List unpacking
a, *b, c = [1, 2, 3, 4, 5]  # a=1, b=[2, 3, 4], c=5

Tuples

Les tuples sont des séquences ordonnées et immuables.

Création

empty_tuple = ()
single_item_tuple = (1,)  # Note the comma
tuple_with_items = (1, 2, 3)
tuple_from_iterable = tuple("abc")

Opérations courantes

# Accessing elements (similar to lists)
first_item = my_tuple[0]
last_item = my_tuple[-1]

# Slicing (similar to lists)
subset = my_tuple[1:4]

# Other operations
length = len(my_tuple)
index = my_tuple.index(2)
count = my_tuple.count(3)

# Tuple unpacking
a, b, c = (1, 2, 3)

Techniques avancées

# Named tuples
from collections import namedtuple
Point = namedtuple('Point', ['x', 'y'])
p = Point(11, y=22)
print(p.x, p.y)

# Tuple as dictionary keys (immutable, so allowed)
dict_with_tuple_keys = {(1, 2): 'value'}

Ensembles

Les ensembles sont des collections non ordonnées d'éléments uniques.

Création

empty_set = set()
set_with_items = {1, 2, 3}
set_from_iterable = set([1, 2, 2, 3, 3])  # {1, 2, 3}
set_comprehension = {x for x in range(10) if x % 2 == 0}

Opérations communes

# Adding elements
my_set.add(4)
my_set.update([5, 6, 7])

# Removing elements
my_set.remove(3)  # Raises KeyError if not found
my_set.discard(3)  # No error if not found
popped_item = my_set.pop()  # Remove and return an arbitrary element

# Other operations
length = len(my_set)
is_member = 2 in my_set

# Set operations
union = set1 | set2
intersection = set1 & set2
difference = set1 - set2
symmetric_difference = set1 ^ set2

Techniques avancées

# Frozen sets (immutable)
frozen = frozenset([1, 2, 3])

# Set comparisons
is_subset = set1 <= set2
is_superset = set1 >= set2
is_disjoint = set1.isdisjoint(set2)

# Set of sets (requires frozenset)
set_of_sets = {frozenset([1, 2]), frozenset([3, 4])}

Dictionnaires

Les dictionnaires sont des mappages mutables de paires clé-valeur.

Création

empty_dict = {}
dict_with_items = {'a': 1, 'b': 2, 'c': 3}
dict_from_tuples = dict([('a', 1), ('b', 2), ('c', 3)])
dict_comprehension = {x: x**2 for x in range(5)}

Opérations communes

# Accessing elements
value = my_dict['key']
value = my_dict.get('key', default_value)

# Adding/Updating elements
my_dict['new_key'] = value
my_dict.update({'key1': value1, 'key2': value2})

# Removing elements
del my_dict['key']
popped_value = my_dict.pop('key', default_value)
last_item = my_dict.popitem()  # Remove and return an arbitrary key-value pair

# Other operations
keys = my_dict.keys()
values = my_dict.values()
items = my_dict.items()
length = len(my_dict)
is_key_present = 'key' in my_dict

Techniques avancées

# Dictionary unpacking
merged_dict = {**dict1, **dict2}

# Default dictionaries
from collections import defaultdict
dd = defaultdict(list)
dd['key'].append(1)  # No KeyError

# Ordered dictionaries (Python 3.7+ dictionaries are ordered by default)
from collections import OrderedDict
od = OrderedDict([('a', 1), ('b', 2), ('c', 3)])

# Counter
from collections import Counter
c = Counter(['a', 'b', 'c', 'a', 'b', 'b'])
print(c.most_common(2))  # [('b', 3), ('a', 2)]

Cordes

Les chaînes sont des séquences immuables de caractères Unicode.

Création

single_quotes = 'Hello'
double_quotes = "World"
triple_quotes = '''Multiline
string'''
raw_string = r'C:\Users\name'
f_string = f"The answer is {40 + 2}"

Opérations communes

# Accessing characters
first_char = my_string[0]
last_char = my_string[-1]

# Slicing (similar to lists)
substring = my_string[1:4]

# String methods
upper_case = my_string.upper()
lower_case = my_string.lower()
stripped = my_string.strip()
split_list = my_string.split(',')
joined = ', '.join(['a', 'b', 'c'])

# Other operations
length = len(my_string)
is_substring = 'sub' in my_string
char_count = my_string.count('a')

Techniques avancées

# String formatting
formatted = "{} {}".format("Hello", "World")
formatted = "%s %s" % ("Hello", "World")

# Regular expressions
import re
pattern = r'\d+'
matches = re.findall(pattern, my_string)

# Unicode handling
unicode_string = u'\u0061\u0062\u0063'

Tableaux

Les tableaux sont des séquences compactes de valeurs numériques (du module array).

Création et utilisation

from array import array
int_array = array('i', [1, 2, 3, 4, 5])
float_array = array('f', (1.0, 1.5, 2.0, 2.5))

# Operations (similar to lists)
int_array.append(6)
int_array.extend([7, 8, 9])
popped_value = int_array.pop()

Piles

Les piles peuvent être implémentées à l'aide de listes ou de collections.deque.

Mise en œuvre et utilisation

# Using list
stack = []
stack.append(1)  # Push
stack.append(2)
top_item = stack.pop()  # Pop

# Using deque (more efficient)
from collections import deque
stack = deque()
stack.append(1)  # Push
stack.append(2)
top_item = stack.pop()  # Pop

Files d'attente

Les files d'attente peuvent être implémentées à l'aide de collections.deque ou queue.Queue.

Mise en œuvre et utilisation

# Using deque
from collections import deque
queue = deque()
queue.append(1)  # Enqueue
queue.append(2)
first_item = queue.popleft()  # Dequeue

# Using Queue (thread-safe)
from queue import Queue
q = Queue()
q.put(1)  # Enqueue
q.put(2)
first_item = q.get()  # Dequeue

Listes liées

Python n'a pas de liste chaînée intégrée, mais elle peut être implémentée.

Mise en œuvre simple

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class LinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        if not self.head:
            self.head = Node(data)
            return
        current = self.head
        while current.next:
            current = current.next
        current.next = Node(data)

Arbres

Les arbres peuvent être implémentés à l'aide de classes personnalisées.

Implémentation simple d’un arbre binaire

class TreeNode:
    def __init__(self, value):
        self.value = value
        self.left = None
        self.right = None

class BinaryTree:
    def __init__(self, root):
        self.root = TreeNode(root)

    def insert(self, value):
        self._insert_recursive(self.root, value)

    def _insert_recursive(self, node, value):
        if value < node.value:
            if node.left is None:
                node.left = TreeNode(value)
            else:
                self._insert_recursive(node.left, value)
        else:
            if node.right is None:
                node.right = TreeNode(value)
            else:
                self._insert_recursive(node.right, value)

Des tas

Les tas peuvent être implémentés à l'aide du module heapq.

Usage

import heapq

# Create a heap
heap = []
heapq.heappush(heap, 3)
heapq.heappush(heap, 1)
heapq.heappush(heap, 4)

# Pop smallest item
smallest = heapq.heappop(heap)

# Create a heap from a list
my_list = [3, 1, 4, 1, 5, 9]
heapq.heapify(my_list)

Graphiques

Les graphiques peuvent être implémentés à l'aide de dictionnaires.

Mise en œuvre simple

class Graph:
    def __init__(self):
        self.graph = {}

    def add_edge(self, u, v):
        if u not in self.graph:
            self.graph[u] = []
        self.graph[u].append(v)

    def bfs(self, start):
        visited = set()
        queue = [start]
        visited.add(start)
        while queue:
            vertex = queue.pop(0)
            print(vertex, end=' ')
            for neighbor in self.graph.get(vertex, []):
                if neighbor not in visited:
                    visited.add(neighbor)
                    queue.append(neighbor)

Structures de données avancées

Essayer

class TrieNode:
    def __init__(self):
        self.children = {}
        self.is_end = False

class Trie:
    def __init__(self):
        self.root = TrieNode()

    def insert(self, word):
        node = self.root
        for char in word:
            if char not in node.children:
                node.children[char] = TrieNode()
            node = node.children[char]
        node.is_end = True

    def search(self, word):
        node = self.root
        for char in word:
            if char not in node.children:
                return False
            node = node.children[char]
        return node.is_end

Ensemble disjoint (Union-Recherche)

class DisjointSet:
    def __init__(self, vertices):
        self.parent = {v: v for v in vertices}
        self.rank = {v: 0 for v in vertices}

    def find(self, item):
        if self.parent[item] != item:
            self.parent[item] = self.find(self.parent[item])
        return self.parent[item]

    def union(self, x, y):
        xroot = self.find(x)
        yroot = self.find(y)
        if self.rank[xroot] < self.rank[yroot]:
            self.parent[xroot] = yroot
        elif self.rank[xroot] > self.rank[yroot]:
            self.parent[yroot] = xroot
        else:
            self.parent[yroot] = xroot
            self.rank[xroot] += 1

Cette aide-mémoire complète couvre un large éventail de structures de données Python, depuis les types intégrés de base jusqu'aux implémentations personnalisées plus avancées. Chaque section comprend des méthodes de création, des opérations courantes et des techniques avancées, le cas échéant.
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