什么是python中列表的推导式？

什么是python中列表的推导式？

生成一个数字列表：

python

numbers = [x for x in range(10)]

print(numbers) # 输出: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

生成一个数字列表的平方：

python

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：

python

even_numbers = [x for x in range(10) if x % 2 == 0]

print(even_numbers) # 输出: [0, 2, 4, 6, 8]

从字符串列表中提取长度：

python

words = ["apple", "banana", "cherry", "date"]

word_lengths = [len(word) for word in words]

print(word_lengths) # 输出: [5, 6, 6, 4]

使用条件表达式修改元素：

python

mixed_list = [1, 2, "three", 4, "five"]

modified_list = [x if isinstance(x, int) else 0 for x in mixed_list]

print(modified_list) # 输出: [1, 2, 0, 4, 0]

嵌套列表推导式：

python

matrix = [[i for i in range(3)] for _ in range(3)]

print(matrix) # 输出: [[0, 1, 2], [0, 1, 2], [0, 1, 2]]

使用函数对列表元素进行转换：

python

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

squared_numbers = [math.sqrt(x) for x in numbers]

print(squared_numbers) # 输出: [1.0, 1.4142135623730951, 1.7320508075688772, 2.0, 2.23606797749979]

嵌套循环的列表推导式：

python

pairs = [(x, y) for x in range(3) for y in range(3)]

print(pairs) # 输出: [(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]

使用条件过滤嵌套循环的列表推导式：

python

pairs = [(x, y) for x in range(3) for y in range(3) if x != y]

print(pairs) # 输出: [(0, 1), (0, 2), (1, 0), (1, 2), (2, 0), (2, 1)]

字典推导式：

python

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

inverted_dict = {value: key for key, value in original_dict.items()}

print(inverted_dict) # 输出: {1: 'a', 2: 'b', 3: 'c'}2024-11-03