串列（List）#

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# 建立串列
numbers = [1, 2, 3, 4, 5]
fruits = ["apple", "banana", "cherry"]
mixed = [1, "hello", 3.14, True]  # 不同型別也可以
empty = []  # 空串列

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fruits = ["apple", "banana", "cherry", "date"]
#          0         1         2         3
#         -4        -3        -2        -1

print(fruits[0])   # apple
print(fruits[2])   # cherry
print(fruits[-1])  # date（最後一個）
print(fruits[-2])  # cherry（倒數第二個）

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nums = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

print(nums[2:5])    # [2, 3, 4]
print(nums[:4])     # [0, 1, 2, 3]
print(nums[6:])     # [6, 7, 8, 9]
print(nums[::2])    # [0, 2, 4, 6, 8]（每隔一個）
print(nums[::-1])   # [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]（反轉）

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

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fruits = ["apple", "banana"]

# append()：加到尾端
fruits.append("cherry")
print(fruits)  # ['apple', 'banana', 'cherry']

# insert()：插入到指定位置
fruits.insert(1, "mango")
print(fruits)  # ['apple', 'mango', 'banana', 'cherry']

# extend()：合併另一個串列
more = ["date", "elderberry"]
fruits.extend(more)
print(fruits)  # ['apple', 'mango', 'banana', 'cherry', 'date', 'elderberry']

# 或用 + 串接（產生新串列）
new_list = fruits + ["fig"]

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fruits = ["apple", "banana", "cherry", "banana"]

# remove()：刪除第一個符合的值
fruits.remove("banana")
print(fruits)  # ['apple', 'cherry', 'banana']

# pop()：刪除並回傳指定索引的元素（預設最後一個）
last = fruits.pop()
print(last)    # banana
print(fruits)  # ['apple', 'cherry']

# pop(index)：刪除指定索引
item = fruits.pop(0)
print(item)    # apple

# del：刪除指定索引或切片
nums = [1, 2, 3, 4, 5]
del nums[2]
print(nums)  # [1, 2, 4, 5]

del nums[1:3]
print(nums)  # [1, 5]

# clear()：清空串列
nums.clear()
print(nums)  # []

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fruits = ["apple", "banana", "cherry", "banana"]

# 是否存在
print("banana" in fruits)     # True
print("mango" not in fruits)  # True

# 計數
print(fruits.count("banana"))  # 2

# 找索引（第一個符合的）
print(fruits.index("cherry"))  # 2

# 長度
print(len(fruits))  # 4

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numbers = [3, 1, 4, 1, 5, 9, 2, 6]

# sort()：原地排序（修改原串列）
numbers.sort()
print(numbers)  # [1, 1, 2, 3, 4, 5, 6, 9]

# 由大到小
numbers.sort(reverse=True)
print(numbers)  # [9, 6, 5, 4, 3, 2, 1, 1]

# sorted()：回傳新串列，不修改原串列
original = [3, 1, 4, 1, 5]
new = sorted(original)
print(original)  # [3, 1, 4, 1, 5]（不變）
print(new)       # [1, 1, 3, 4, 5]

# 自訂排序規則（用 key）
words = ["banana", "apple", "cherry", "kiwi"]
words.sort(key=len)           # 依長度排序
print(words)  # ['kiwi', 'apple', 'banana', 'cherry']

words.sort(key=lambda w: w[-1])  # 依最後一個字母排序

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nums = [1, 2, 3, 4, 5]

nums.reverse()
print(nums)  # [5, 4, 3, 2, 1]

# 也可以用切片（產生新串列）
reversed_nums = nums[::-1]

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a = [1, 2, 3]

# 直接賦值：兩個變數指向同一個物件
b = a
b.append(4)
print(a)  # [1, 2, 3, 4]（a 也被修改了！）

# 淺複製：產生新物件
c = a.copy()        # 方法一
d = list(a)         # 方法二
e = a[:]            # 方法三

c.append(5)
print(a)  # [1, 2, 3, 4]（a 不受影響）
print(c)  # [1, 2, 3, 4, 5]

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squares = []
for x in range(1, 6):
    squares.append(x ** 2)
print(squares)  # [1, 4, 9, 16, 25]

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squares = [x ** 2 for x in range(1, 6)]
print(squares)  # [1, 4, 9, 16, 25]

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# 只取偶數
even = [x for x in range(10) if x % 2 == 0]
print(even)  # [0, 2, 4, 6, 8]

# 只取大於 3 的平方
big_squares = [x ** 2 for x in range(1, 8) if x > 3]
print(big_squares)  # [16, 25, 36, 49]

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nums = [1, 2, 3, 4, 5, 6]

# if 在後面 → 篩選（只保留偶數）
keep_even   = [x for x in nums if x % 2 == 0]
print(keep_even)   # [2, 4, 6]

# if-else 在前面 → 轉換（每個元素都保留，但奇數變 0）
mark_even   = [x if x % 2 == 0 else 0 for x in nums]
print(mark_even)   # [0, 2, 0, 4, 0, 6]

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matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# 等同於兩層 for 迴圈：先走 row，再走 row 裡的 num
flat = [num for row in matrix for num in row]
print(flat)  # [1, 2, 3, 4, 5, 6, 7, 8, 9]

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nums = [3, 1, 4, 1, 5, 9, 2, 6]

print(sum(nums))    # 31  → 所有元素相加
print(max(nums))    # 9   → 最大值
print(min(nums))    # 1   → 最小值
print(len(nums))    # 8   → 元素個數

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print(sum(nums, 100))   # 131（從 100 開始累加）

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words = ["banana", "apple", "kiwi", "cherry"]

print(max(words))              # kiwi（預設依字母序）
print(max(words, key=len))     # banana（依長度取最長）
print(min(words, key=len))     # kiwi（依長度取最短）

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nums = [3, 1, 4, 1, 5]

new = sorted(nums)               # 升冪，回傳新串列
print(nums)   # [3, 1, 4, 1, 5]（原串列不變）
print(new)    # [1, 1, 3, 4, 5]

desc = sorted(nums, reverse=True)
print(desc)   # [5, 4, 3, 1, 1]

rev = list(reversed(nums))
print(rev)    # [5, 1, 4, 1, 3]

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fruits = ["apple", "banana", "cherry"]

# enumerate：常用於需要編號的迴圈
for i, fruit in enumerate(fruits, start=1):
    print(f"{i}. {fruit}")
# 1. apple
# 2. banana
# 3. cherry

# zip：把兩個串列合併成鍵值對
prices = [30, 15, 25]
for fruit, price in zip(fruits, prices):
    print(f"{fruit}: {price} 元")
# apple: 30 元
# banana: 15 元
# cherry: 25 元

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a = [1, 2, 3, 4]
b = ["x", "y"]
print(list(zip(a, b)))   # [(1, 'x'), (2, 'y')]

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scores = [85, 92, 78, 60, 95]

print(any(s >= 90 for s in scores))   # True（92、95 符合）
print(all(s >= 60 for s in scores))   # True（全部及格）
print(all(s >= 80 for s in scores))   # False（60、78 不符合）

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# 字串 → 串列
chars = list("Python")
print(chars)   # ['P', 'y', 't', 'h', 'o', 'n']

# range → 串列
r = list(range(5))
print(r)       # [0, 1, 2, 3, 4]

# tuple → 串列
t = list((1, 2, 3))
print(t)       # [1, 2, 3]

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numbers = [1, 2, 2, 3, 3, 3, 4]
unique = list(set(numbers))
print(sorted(unique))  # [1, 2, 3, 4]

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nested = [[1, 2], [3, 4], [5, 6]]
flat = [x for sublist in nested for x in sublist]
print(flat)  # [1, 2, 3, 4, 5, 6]

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numbers = range(1, 11)
even = [n for n in numbers if n % 2 == 0]
odd = [n for n in numbers if n % 2 != 0]
print(even)  # [2, 4, 6, 8, 10]
print(odd)   # [1, 3, 5, 7, 9]