python基础之列表推导式

Posted 2021-01-09 RobotsRising

1、列表推导式

1.1、求0~29之间能被3整除的数

ret = [i for i in range(30) if i%3 ==0]
print(ret)

　　输出结果：

[0, 3, 6, 9, 12, 15, 18, 21, 24, 27]

2、字典推导式

2.1、将字典mcase = {‘a‘: 10, ‘b‘: 34}的key、value互换位置

mcase = {‘a‘: 10, ‘b‘: 34}

mcase_frequency = {mcase[k]: k for k in mcase}
print(mcase_frequency)

　　输出结果：

{10: ‘a‘, 34: ‘b‘}

2.2、将字典中大小写key的value值相加

mcase = {‘a‘: 10, ‘b‘: 34, ‘A‘: 7, ‘Z‘: 3}
mcase_frequency = {k.lower(): mcase.get(k.lower(), 0) + mcase.get(k.upper(), 0) for k in mcase}
print(mcase_frequency)

　　输出结果：

{‘a‘: 17, ‘b‘: 34, ‘z‘: 3}

3、集合生成式

3.1、求列表[1, -1, 2]中元素的平方值的集合

squared = {x**2 for x in [1, -1, 2]}
print(squared)

　　输出结果：

{1, 4}