三种方法：
①直接使用dict
②使用defaultdict
③使用Counter

一、直接使用dict

text = "I'm a hand some boy!"
frequency = {}
for word in text.split():
    if word not in frequency:
        frequency[word] = 1
        else:
            frequency[word] += 1

二、使用defaultdict

import collections
frequency = collections.defaultdict(int)
text = "I'm a hand some boy!"
for word in text.split():
    frequency[word] += 1

三、使用Counter

import collections
text = "I'm a hand some boy!"
frequency = collections.Counter(text.split())