代码简洁

避免使用完整的函数定义，特别适合小型操作

即用即弃

不需要命名和存储，用完即弃，不污染命名空间

高阶函数搭档

与map()、filter()、sorted()等函数完美配合

# 平方计算
square = lambda x: x ** 2
print(square(5))  # 输出: 25

# 加法计算
add = lambda a, b: a + b
print(add(10, 7))  # 输出: 17

# 按字符串长度排序
words = ["apple", "banana", "cherry", "date"]
sorted_words = sorted(words, key=lambda word: len(word))
print(sorted_words)  # 输出: ['date', 'apple', 'banana', 'cherry']

# 按元组第二个元素排序
pairs = [(1, 9), (2, 5), (3, 7)]
sorted_pairs = sorted(pairs, key=lambda pair: pair[1])
print(sorted_pairs)  # 输出: [(2, 5), (3, 7), (1, 9)]

# 过滤偶数
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]
even_numbers = list(filter(lambda x: x % 2 == 0, numbers))
print(even_numbers)  # 输出: [2, 4, 6, 8]

# 过滤空字符串
words = ["hello", "", "world", " ", "python", None]
valid_words = list(filter(lambda s: s and s.strip(), words))
print(valid_words)  # 输出: ['hello', 'world', 'python']

# 转换为平方数
numbers = [1, 2, 3, 4, 5]
squares = list(map(lambda x: x ** 2, numbers))
print(squares)  # 输出: [1, 4, 9, 16, 25]

# 字符串首字母大写
names = ["alice", "bob", "charlie"]
capitalized = list(map(lambda name: name.capitalize(), names))
print(capitalized)  # 输出: ['Alice', 'Bob', 'Charlie']

# 自定义排序
students = [
    {"name": "Alice", "grade": 90},
    {"name": "Bob", "grade": 78},
    {"name": "Charlie", "grade": 95}
]

# 按成绩降序排序
students_sorted = sorted(students, key=lambda s: s["grade"], reverse=True)
print(students_sorted)
# 输出: [{'name': 'Charlie', 'grade': 95}, {'name': 'Alice', 'grade': 90}, {'name': 'Bob', 'grade': 78}]