标签:strong 表示 首字母 [] ice python 相同 for str
列表推导:
类似for循环,是从其他列表创建列表的方式
s = [i for i in range(6)] print(s) # [0, 1, 2, 3, 4, 5]
可以加判断条件
s = [i for i in range(6) if i%2 == 0] print(s) # [0, 2, 4]
可以有更多的for
s = [(x, y) for x in range(3) for y in range(3)] print(s) # [(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]
将首字符相同的男孩与女孩名字配对
girls =[‘alice‘,‘bernice‘,‘clarice‘] boys =[‘chris‘, ‘arnold‘, ‘bob‘] li = [b + "+" + g for b in boys for g in girls if b[0] == g[0]] print(li)
上面的效率不高,因为需要检查每一种配对,优化后:
girls =[‘alice‘,‘bernice‘,‘clarice‘] boys =[‘chris‘, ‘arnold‘, ‘bob‘] d = {} for girl in girls: d.setdefault(girl[0], []).append(girl) print([b + "+" + g for b in boys for g in d[b[0]]]) # 创建字典d,每项的键都是一个字母,值为这个字母开头的女孩名组成的列表,列表推导遍历男孩,找到名字首字母和当前男孩相同的女孩
字典推导:
字典推导中,for前面有两个用冒号分隔的表达式,分别表示键和值;列表只有一个
d = {i: "{} +1 is {}".format(i, i+1) for i in range(6)} print(d) # {0: ‘0 +1 is 1‘, 1: ‘1 +1 is 2‘, 2: ‘2 +1 is 3‘, 3: ‘3 +1 is 4‘, 4: ‘4 +1 is 5‘, 5: ‘5 +1 is 6‘}
标签:strong 表示 首字母 [] ice python 相同 for str
原文地址:https://www.cnblogs.com/Mr-chenshuai/p/10034247.html