Pythonic式的实现列表/字典理解的方法

[expression for item in iterable if condition]

# 创建一个包含0到9平方的列表
squares = [x**2 for x in range(10)]
print(squares)  # 输出: [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

# 过滤出偶数的平方
even_squares = [x**2 for x in range(10) if x % 2 == 0]
print(even_squares)  # 输出: [0, 4, 16, 36, 64]

{key_expression: value_expression for item in iterable if condition}

# 创建一个字典，键为0到9，值为它们的平方
squares_dict = {x: x**2 for x in range(10)}
print(squares_dict)  # 输出: {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}

# 过滤出偶数键和它们的平方
even_squares_dict = {x: x**2 for x in range(10) if x % 2 == 0}
print(even_squares_dict)  # 输出: {0: 0, 2: 4, 4: 16, 6: 36, 8: 64}

# 生成器表达式不会立即生成整个列表，而是返回一个生成器对象
squares_gen = (x**2 for x in range(10))

# 逐个获取值
for square in squares_gen:
    print(square)  # 输出: 0 1 4 9 16 25 36 49 64 81