s = "Hello"

# 方式1: for循環(huán)直接遍歷
for char in s:
    print(char)  # H e l l o

# 方式2: 使用索引遍歷
for i in range(len(s)):
    print(f"索引{i}: {s[i]}")

s = "Hello"

# enumerate() 獲取索引和值
for index, char in enumerate(s):
    print(f"位置{index}: {char}")
    
# 從指定索引開始
for index, char in enumerate(s, start=1):
    print(f"第{index}個(gè)字符: {char}")

s = "Hello"

# reversed() 反向遍歷
for char in reversed(s):
    print(char)  # o l l e H

# 使用索引反向
for i in range(len(s)-1, -1, -1):
    print(s[i])

s = "Hello World"

# 遍歷部分字符串
for char in s[6:]:  # 從第6個(gè)字符開始
    print(char)  # W o r l d

# 步長遍歷
for char in s[::2]:  # 每隔一個(gè)字符
    print(char)  # H l o W r d

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

# 直接遍歷
for item in my_list:
    print(item)

# 使用索引遍歷
for i in range(len(my_list)):
    print(f"索引{i}: {my_list[i]}")

my_list = ['apple', 'banana', 'cherry']

for index, value in enumerate(my_list):
    print(f"第{index}個(gè)水果: {value}")

# 指定起始索引
for index, value in enumerate(my_list, start=1):
    print(f"水果{index}: {value}")

my_list = [1, 2, 3, 4, 5]
i = 0
while i < len(my_list):
    print(my_list[i])
    i += 1

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

# 遍歷并處理（創(chuàng)建新列表）
squares = [x**2 for x in my_list]
print(squares)  # [1, 4, 9, 16, 25]

# 帶條件的遍歷
evens = [x for x in my_list if x % 2 == 0]
print(evens)  # [2, 4]

names = ['Alice', 'Bob', 'Charlie']
scores = [85, 92, 78]

# 同時(shí)遍歷兩個(gè)列表
for name, score in zip(names, scores):
    print(f"{name}: {score}分")

# 使用enumerate + zip
for i, (name, score) in enumerate(zip(names, scores)):
    print(f"第{i+1}名: {name} - {score}分")

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

# reversed() 反向遍歷
for item in reversed(my_list):
    print(item)  # 5 4 3 2 1

# 使用切片反向
for item in my_list[::-1]:
    print(item)  # 5 4 3 2 1

my_tuple = (1, 2, 3, 4, 5)

# 直接遍歷
for item in my_tuple:
    print(item)

# enumerate遍歷
for i, item in enumerate(my_tuple):
    print(f"第{i}個(gè)元素: {item}")

# 反向遍歷
for item in reversed(my_tuple):
    print(item)

my_set = {1, 2, 3, 4, 5}

# 直接遍歷（集合無序，遍歷順序不確定）
for item in my_set:
    print(item)

# 注意：集合沒有索引，不能使用索引遍歷

my_set = {5, 3, 1, 4, 2}

# 排序后遍歷
for item in sorted(my_set):
    print(item)  # 1 2 3 4 5

# 反向排序遍歷
for item in sorted(my_set, reverse=True):
    print(item)  # 5 4 3 2 1

my_set = {'apple', 'banana', 'cherry'}

# 遍歷時(shí)檢查
for fruit in my_set:
    if 'a' in fruit:
        print(f"{fruit} 包含字母'a'")

my_dict = {'name': 'Alice', 'age': 25, 'city': 'Beijing'}

# 直接遍歷鍵（默認(rèn)方式）
for key in my_dict:
    print(f"鍵: {key}")

# 顯式使用keys()
for key in my_dict.keys():
    print(f"鍵: {key}")

my_dict = {'name': 'Alice', 'age': 25, 'city': 'Beijing'}

# 遍歷值
for value in my_dict.values():
    print(f"值: {value}")

my_dict = {'name': 'Alice', 'age': 25, 'city': 'Beijing'}

# 同時(shí)獲取鍵和值
for key, value in my_dict.items():
    print(f"{key}: {value}")
    
# 輸出：
# name: Alice
# age: 25
# city: Beijing

my_dict = {'name': 'Alice', 'age': 25, 'city': 'Beijing'}

# 遍歷items并獲取索引
for i, (key, value) in enumerate(my_dict.items()):
    print(f"第{i}項(xiàng): {key} = {value}")

my_dict = {'b': 2, 'a': 1, 'c': 3}

# 按鍵排序遍歷
for key in sorted(my_dict):
    print(f"{key}: {my_dict[key]}")

# 按值排序遍歷
for key in sorted(my_dict, key=my_dict.get):
    print(f"{key}: {my_dict[key]}")
    
# 反向排序遍歷
for key in sorted(my_dict, reverse=True):
    print(f"{key}: {my_dict[key]}")

my_dict = {'a': 1, 'b': 2, 'c': 3}

# 遍歷并創(chuàng)建新字典
squared = {k: v**2 for k, v in my_dict.items()}
print(squared)  # {'a': 1, 'b': 4, 'c': 9}

# 帶條件的遍歷
filtered = {k: v for k, v in my_dict.items() if v > 1}
print(filtered)  # {'b': 2, 'c': 3}

dict1 = {'a': 1, 'b': 2}
dict2 = {'a': 10, 'b': 20}

# 遍歷相同的鍵
for key in dict1:
    if key in dict2:
        print(f"{key}: {dict1[key]} + {dict2[key]} = {dict1[key] + dict2[key]}")

# 列表過濾遍歷
numbers = [1, 2, 3, 4, 5, 6]
for num in filter(lambda x: x % 2 == 0, numbers):
    print(num)  # 2 4 6

# 字典過濾遍歷
my_dict = {'a': 1, 'b': 2, 'c': 3}
for k, v in filter(lambda item: item[1] > 1, my_dict.items()):
    print(f"{k}: {v}")  # b: 2, c: 3

# 列表映射遍歷
numbers = [1, 2, 3]
for num in map(lambda x: x**2, numbers):
    print(num)  # 1 4 9

# 內(nèi)存友好的大列表遍歷
numbers = range(1000000)  # 不立即創(chuàng)建列表

# 使用生成器表達(dá)式
sum_squares = sum(x**2 for x in numbers if x % 2 == 0)
print(sum_squares)

# 遍歷生成器
for square in (x**2 for x in range(5)):
    print(square)  # 0 1 4 9 16

from itertools import chain, product, permutations

# 連接多個(gè)可迭代對(duì)象
list1 = [1, 2, 3]
list2 = ['a', 'b', 'c']
for item in chain(list1, list2):
    print(item)  # 1 2 3 a b c

# 笛卡爾積
colors = ['紅', '藍(lán)']
sizes = ['S', 'M']
for color, size in product(colors, sizes):
    print(f"{color}{size}")  # 紅S 紅M 藍(lán)S 藍(lán)M

# 排列
for p in permutations('ABC', 2):
    print(p)  # ('A', 'B') ('A', 'C') ('B', 'A') ('B', 'C') ('C', 'A') ('C', 'B')