Python数据容器全指南:列表、元组、集合与字典一文搞懂

fruits = ['apple', 'banana', 'orange']
numbers = [1, 2, 3, 4, 5]
mixed = [1, 'text', True, 3.14]

coordinates = (10, 20)
colors = ('red', 'green', 'blue')

unique_numbers = {1, 2, 3, 3, 4}  # 结果为{1, 2, 3, 4}

person = {'name': 'Alice', 'age': 25, 'city': 'New York'}

# 列表转元组
my_list = [1, 2, 3]
my_tuple = tuple(my_list)

# 元组转列表
my_tuple = (1, 2, 3)
my_list = list(my_tuple)

# 列表转集合（去重）
my_list = [1, 2, 2, 3]
my_set = set(my_list)

# 字典的特殊转换
my_dict = {'a': 1, 'b': 2}
keys_list = list(my_dict.keys())
values_list = list(my_dict.values())

squares = [x**2 for x in range(10)]

square_dict = {x: x**2 for x in range(5)}

unique_lengths = {len(word) for word in ['hello', 'world', 'python']}

# 列表嵌套
matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# 字典嵌套
employees = {
    'Alice': {'age': 25, 'position': 'Developer'},
    'Bob': {'age': 30, 'position': 'Manager'}
}

# 访问嵌套元素
print(matrix[1][2])  # 输出6
print(employees['Alice']['position'])  # 输出'Developer'

# 浅拷贝示例
original = [[1, 2], [3, 4]]
shallow_copy = original.copy()
shallow_copy[0][0] = 99  # 会影响original!

# 解决方案：使用深拷贝
import copy
deep_copy = copy.deepcopy(original)

sales = [
    {'product': 'A', 'amount': 100, 'region': 'East'},
    {'product': 'B', 'amount': 200, 'region': 'West'},
    # ...更多数据
]

# 按地区分组
from collections import defaultdict
region_sales = defaultdict(list)
for sale in sales:
    region_sales[sale['region']].append(sale)

# 计算每个产品的总销售额
product_totals = {}
for sale in sales:
    product = sale['product']
    product_totals[product] = product_totals.get(product, 0) + sale['amount']

def two_sum(nums, target):
    seen = {}
    for i, num in enumerate(nums):
        complement = target - num
        if complement in seen:
            return [seen[complement], i]
        seen[num] = i
    return []

import json

# 读取配置
with open('config.json') as f:
    config = json.load(f)

# 修改配置
config['timeout'] = 30

# 保存配置
with open('config.json', 'w') as f:
    json.dump(config, f, indent=4)

from collections import defaultdict, Counter

# defaultdict示例
word_counts = defaultdict(int)
for word in words:
    word_counts[word] += 1

# Counter示例
sales_count = Counter(product['name'] for product in sales_data)

# 不好的做法
result = []
for i in range(10000):
    result.append(i)

# 更好的做法
result = [0] * 10000
for i in range(10000):
    result[i] = i

# 列表推导式（立即计算）
big_list = [x**2 for x in range(1000000)]  # 占用大量内存

# 生成器表达式（惰性计算）
big_gen = (x**2 for x in range(1000000))  # 内存友好

# 传统写法
if key not in my_dict:
    my_dict[key] = []
my_dict[key].append(value)

# 使用setdefault
my_dict.setdefault(key, []).append(value)