[exp for iter_var in iterable (if conditional)]
原理:
优先于for和if循环:
# 实现[1,2,3,4,5]的列表 alist1 = list(range(1,6)) print(alist1) # 实现[1,4,9,16,25,36,49]的列表 alist2 = [] for i in range(1,8): alist2.append(i*i) print(alist2) # 用一行实现 alist = [i*i for i in range(1,8)] print(alist) #结果: [1, 2, 3, 4, 5] [1, 4, 9, 16, 25, 36, 49] [1, 4, 9, 16, 25, 36, 49]
list2 = [x+y for x in range(1,5) for y in range(1,6)] #结果: [2, 3, 4, 5, 6, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 5, 6, 7, 8, 9]
list3 = [x for x in range(1,10) if x>5] print(list3) #结果: [6, 7, 8, 9]
L = ['Heli','JACK','ab'] l1 = [i.lower() for i in L] print(l1) #结果: ['heli', 'jack', 'ab']
zip生成列表,生成字典
zip()函数接受一系列可迭代对象作为参数,将不同对象中相对应的元素打包成一个元组(tuple),返回由这些元组组成的list列表
l1 = [1,3,6] l2 = [5,8,9] for (x,y) in zip(l1,l2): print(x,y,x+y) #结果: 1 5 6 3 8 11 6 9 15 keys = ['a','c','f'] vals = [1,7,3] D2 = {} for (k,v) in zip(keys,vals): D2[k]=v print(D2) #结果:{'a': 1, 'c': 7, 'f': 3}
enumerate() 函数用于将一个可遍历的数据对象(如列表、元组或字符串)组合为一个索引序列,同时列出数据和数据下标,一般用在for循环中
enumerate(seq, [start=0]) ,返回枚举对象
seasons = ['spring', 'summer', 'winter'] a = list(enumerate(seasons)) for i,element in enumerate(seasons): print(i,element) #结果: 0 spring 1 summer 2 winter
关于filter 、 reduce,具体可查看上一篇文章