# 傳統(tǒng)寫(xiě)法
squares = []
for x in range(10):
    if x % 2 == 0:
        squares.append(x**2)
 
# 列表推導(dǎo)式
squares = [x**2 for x in range(10) if x % 2 == 0]  # 輸出：[0, 4, 16, 36, 64]

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
transpose = [[row[i] for row in matrix] for i in range(3)]  
# 輸出：[[1,4,7], [2,5,8], [3,6,9]]

colors = ["red", "blue"]
sizes = ["S", "M", "L"]
products = [f"{c}-{s}" for c in colors for s in sizes]  
# 輸出：['red-S', 'red-M', ..., 'blue-L']

nested_list = [[1, 2], [3, 4, 5], [6]]
flat_list = [num for sublist in nested_list for num in sublist]  
# 輸出：[1, 2, 3, 4, 5, 6]

numbers = [1, 2, 3, 4, 5]
flags = ["even" if x % 2 == 0 else "odd" for x in numbers]  
# 輸出：['odd', 'even', 'odd', 'even', 'odd']

data = ["10", "20", "abc", "30"]
converted = [int(x) if x.isdigit() else 0 for x in data]  
# 輸出：[10, 20, 0, 30]

scores = [85, 92, 78, 65, 95]
grades = ["A" if s >= 90 else "B" if s >= 80 else "C" for s in scores]  
# 輸出：['B', 'A', 'B', 'C', 'A']

def calculate_discount(price, is_vip):
    return price * 0.8 if is_vip else price * 0.9
 
prices = [100, 200, 150]
vip_status = [True, False, True]
final_prices = [calculate_discount(p, v) for p, v in zip(prices, vip_status)]  
# 輸出：[80.0, 180.0, 120.0]

import re
 
logs = ["Error: File not found", "Warning: Low disk space", "Info: System ready"]
errors = [log for log in logs if re.search(r"Error", log)]  
# 輸出：['Error: File not found']

# 鍵值對(duì)交換
original_dict = {"a": 1, "b": 2, "c": 3}
swapped_dict = {value: key for key, value in original_dict.items()}  
# 輸出：{1: 'a', 2: 'b', 3: 'c'}
 
# 條件過(guò)濾
employees = [{"name": "張三", "salary": 15000}, {"name": "李四", "salary": 28000}]
high_earners = {e["name"]: e["salary"] for e in employees if e["salary"] > 20000}  
# 輸出：{'李四': 28000}

# 字符串去重
text = "hello world"
unique_chars = {char for char in text}  
# 輸出：{'h', 'e', 'l', 'o', ' ', 'w', 'r', 'd'}（順序隨機(jī)）
 
# 數(shù)學(xué)運(yùn)算去重
numbers = [1, 2, 2, 3, 4, 4, 5]
squares_set = {x**2 for x in numbers}  
# 輸出：{1, 4, 9, 16, 25}

# 內(nèi)存消耗對(duì)比
big_list = [x**2 for x in range(1000000)]  # 占用大量?jī)?nèi)存
big_gen = (x**2 for x in range(1000000))  # 惰性計(jì)算，節(jié)省內(nèi)存

# 低效寫(xiě)法（每次循環(huán)都調(diào)用函數(shù)）
result = [complex_calculation(x) for x in data if expensive_check(x)]
 
# 高效寫(xiě)法（先過(guò)濾再計(jì)算）
filtered_data = [x for x in data if expensive_check(x)]
result = [complex_calculation(x) for x in filtered_data]

# 列表推導(dǎo)式 vs map/filter
numbers = [1, 2, 3, 4]
 
# 列表推導(dǎo)式（更直觀）
squares1 = [x**2 for x in numbers]
 
# map函數(shù)
squares2 = list(map(lambda x: x**2, numbers))
 
# 復(fù)合操作（推導(dǎo)式優(yōu)勢(shì)明顯）
result1 = [x.upper() + "!" for x in ["a", "b", "c"] if len(x) > 0]
result2 = list(map(lambda x: x.upper() + "!", filter(lambda n: len(n) > 0, ["a", "b", "c"])))

with open("data.txt", "r") as file:
    line_lengths = [len(line.strip()) for line in file if line.strip()]

points = [(x, y) for x in range(-4, 5) for y in range(-4, 5) if x**2 + y**2 < 25]

raw_data = [{"name": "Alice", "age": 25}, {"name": "Bob"}, {"name": "Charlie", "age": 30}]
processed_data = [{k: v for k, v in d.items() if v is not None} for d in raw_data]
# 輸出：[{'name': 'Alice', 'age': 25}, {'name': 'Bob'}, {'name': 'Charlie', 'age': 30}]

x = 10
result = [x**2 for x in range(5)]
print(x)  # 輸出：10（外部x未被修改）

data = ["10", "20", "abc", "30"]
 
# 安全寫(xiě)法
safe_data = []
for item in data:
    try:
        safe_data.append(int(item))
    except ValueError:
        safe_data.append(0)
 
# 推導(dǎo)式替代方案（需配合輔助函數(shù)）
def safe_convert(x):
    try:
        return int(x)
    except ValueError:
        return 0
 
result = [safe_convert(x) for x in data]

# 難以理解的嵌套推導(dǎo)式
result = [[[x for x in range(y)] for y in range(z)] for z in range(5)]
 
# 應(yīng)改寫(xiě)為
result = []
for z in range(5):
    layer = []
    for y in range(z):
        inner = []
        for x in range(y):
            inner.append(x)
        layer.append(inner)
    result.append(layer)

# 假設(shè)性示例（未來(lái)可能支持）
data = [1, 2, 3, "a", "b"]
result = [x**2 if isinstance(x, int) else x.upper() for x in data]
同時(shí)，類型注解與推導(dǎo)式的結(jié)合也在探索中：

python
# Python 3.10+ 類型注解示例
def process_data(numbers: list[int]) -> list[float]:
    return [x * 1.1 for x in numbers]