推导式
ret = [i for i in range(1,11) if i%2 == 0 ] print(ret) #[2, 4, 6, 8, 10]
例二:10以内可以被2整除的数的平方
ret = [i*i for i in range(1,11) if i%2 == 0] print(ret) # [4, 16, 36, 64, 100]
例三:找到嵌套列表中名字含有两个‘e’的所有名字
names = [['Tom', 'Billy', 'Jefferson', 'Andrew', 'Wesley', 'Steven', 'Joe'], ['Alice', 'Jill', 'Ana', 'Wendy', 'Jennifer', 'Sherry', 'Eva']] ret = [ name for lst in names for name in lst if name.count('e') >= 2] print(ret) # ['Jefferson', 'Wesley', 'Steven', 'Jennifer']
例一:将一个字典的key和value对调
mcase = {'a': 10, 'b': 34} mcase_frequency = {mcase[k]: k for k in mcase} print(mcase_frequency) # {10:'a' , 34:'b'}
例二:合并大小写对应的value值,将k统一成小写
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) # {'a':17,'b':34,'z':3}
squared = {x*x for x in [1, -1, 2]} print(squared) # {1, 4}
str_a = "hello" ret = 1000 if len(str_a) >= 3 else 1 print(ret) # 1000