【Pythonリスト】追加・削除・結合・カウント方法まとめ

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# リストの作成
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numbers = [1, 2, 3, 4, 5]
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mixed_list = [1, "apple", 3.5, True]
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print(numbers)      # [1, 2, 3, 4, 5]
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print(mixed_list)   # [1, 'apple', 3.5, True]

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empty_list = []
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another_empty = list()
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print(empty_list)
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print(another_empty)

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fruits = ["apple", "banana"]
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fruits.append("cherry")
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print(fruits)  # ['apple', 'banana', 'cherry']

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fruits = ["apple", "banana", "cherry"]
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fruits.insert(1, "orange")
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print(fruits)  # ['apple', 'orange', 'banana', 'cherry']

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fruits = ["apple", "banana", "cherry"]
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fruits[1] = "orange"
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print(fruits)  # ['apple', 'orange', 'cherry']

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fruits = ["apple", "banana", "apple", "cherry"]
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fruits.remove("apple")
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print(fruits)  # ['banana', 'apple', 'cherry']

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fruits = ["apple", "banana", "cherry"]
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removed = fruits.pop(1)
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print(removed)  # 'banana'
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print(fruits)   # ['apple', 'cherry']

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fruits = ["apple", "banana", "cherry", "kiwi"]
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del fruits[1:3]
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print(fruits)  # ['apple', 'kiwi']

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# インデックス1から3までの要素を取得（終了インデックスは含まれない）
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numbers = [1, 2, 3, 4, 5, 6]
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sub_list = numbers[1:4]
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print(sub_list)  # [2, 3, 4]

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# 2つおきに要素を取得（開始:終了:ステップ）
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numbers = [1, 2, 3, 4, 5, 6]
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step_list = numbers[0:6:2]
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print(step_list)  # [1, 3, 5]

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numbers = [1, 2, 3, 4, 5, 6]
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# 最初の3要素を取得
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first_three = numbers[:3]
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print(first_three)  # [1, 2, 3]
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# 3番目以降の要素を取得
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last_part = numbers[3:]
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print(last_part)  # [4, 5, 6]
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# リスト全体をコピー（新しいリストを作成）
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copy_list = numbers[:]
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print(copy_list)  # [1, 2, 3, 4, 5, 6]

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numbers = [1, 2, 3, 4, 5, 6]
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# リストを逆順に取得
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reversed_list = numbers[::-1]
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print(reversed_list)  # [6, 5, 4, 3, 2, 1]

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fruits = ["apple", "banana", "apple", "cherry"]
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print(fruits.count("apple"))  # 2

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fruits = ["apple", "banana", "apple", "cherry"]
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print(len(fruits))  # 4

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fruits = ["apple", "banana", "apple", "cherry"]
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fruits.extend(["kiwi", "melon"])
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print(fruits)  # ['apple', 'banana', 'apple', 'cherry', 'kiwi', 'melon']

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list1 = [1, 2]
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list2 = [3, 4]
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combined = list1 + list2
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print(combined)  # [1, 2, 3, 4]

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list1 = [1, 2]
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list1.extend([3, 4])
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print(list1)  # [1, 2, 3, 4]
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list1 = [1, 2]
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list2 = [3, 4]
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combined = list1 + list2
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print(list1)  # [1, 2]
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print(list2)  # [3, 4]
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print(combined)  # [1, 2, 3, 4]

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# 1から10までの平方数リストを作成
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squares = [x ** 2 for x in range(1, 11)]
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print(squares)  # [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

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numbers = [5, 2, 9, 1, 7]
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numbers.sort()  # 昇順にソート
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print(numbers)  # [1, 2, 5, 7, 9]
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numbers.sort(reverse=True)  # 降順にソート
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print(numbers)  # [9, 7, 5, 2, 1]

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# リストの作成
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numbers = [9, 7, 5, 2, 1]
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# 指定した要素のインデックスを取得
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index = numbers.index(5)
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print(index)  # 2
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# 指定した要素が含まれているか判定
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exists = 3 in numbers
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print(exists)  # False

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# 2次元リスト
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matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
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print(matrix[1][2])  # 6（2行目の3列目）

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fruits = ["apple", "banana", "cherry"]
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for index, fruit in enumerate(fruits):
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    print(index, fruit)

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names = ["Alice", "Bob"]
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scores = [90, 85]
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for name, score in zip(names, scores):
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    print(f"{name}: {score}")

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import sys
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3
# リストのメモリ使用量を確認
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list_example = [i for i in range(1000)]
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print(sys.getsizeof(list_example))  # リストのメモリサイズ（バイト単位）

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import sys
2

3
# リストを使う場合（メモリを多く消費）
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squares_list = [x ** 2 for x in range(1000000)]
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print(squares_list[0])  # 0
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print(squares_list[1])  # 1
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print(squares_list[2])  # 4
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print(sys.getsizeof(squares_list))  # メモリサイズ（バイト単位）
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# ジェネレータを使う場合（メモリ効率が良い）
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squares_gen = (x ** 2 for x in range(1000000))
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print(next(squares_gen))  # 0
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print(next(squares_gen))  # 1
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print(next(squares_gen))  # 4
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print(sys.getsizeof(squares_gen))  # メモリサイズ（バイト単位）

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# タプルの作成
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tuple_example = (1, 2, 3, "apple")
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print(tuple_example)  # (1, 2, 3, 'apple')
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# インデックスでアクセス可能
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print(tuple_example[1])  # 2
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# 要素の変更は不可（エラーになる）
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tuple_example[1] = 10  # TypeError: 'tuple' object does not support item assignment

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# 辞書の作成
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dict_example = {"name": "Alice", "age": 25, "city": "Tokyo"}
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print(dict_example)  # {'name': 'Alice', 'age': 25, 'city': 'Tokyo'}
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# 値の取得
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print(dict_example["name"])  # Alice
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# 値の変更
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dict_example["age"] = 26
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print(dict_example)  # {'name': 'Alice', 'age': 26, 'city': 'Tokyo'}