小白
import pprintmessage = 'It was a bright cold day in April,\
and the clocks were striking thirteen.'
count = {}
for character in message:
count.setdefault(character, 0)
count = count+1
pprint.pprint(count)
程序为什么可以完成计数功能 dict.setdefault(key, default=None) 方法可以在字典的键不存在时，生成一个键，值为defalut
创建空字典count
自动count的键(key)为字符串，值(value)为出现的次数
源码中遍历字符串message
当字符不在字典中时，生成一个键，键的值默认为0，值+1.如果存在，则不生成新键，值+1
import pprint
message = 'It was a bright cold day in April,\
and the clocks were striking thirteen.'
count = {} #生成空字典
for character in message: #遍历字符串
count.setdefault(character, 0) #当字典中没有字符所对应的键时，生成键，默认值为1
count = count+1 #每当遇到这个字符，这个字符的值会加1
pprint.pprint(count) #打印
页:
[1]