2.统计一句话单词的数量

split()表示用空白切割字符，只能切割字符串

 e="1 2  4    567      100"

>>> e.split()

['1', '2', '4', '567', '100']

>>> e="1 2  4   \n\r 567      \n 100"

>>> e.split()

['1', '2', '4', '567', '100']# \n\r \n都是制表符不可见字符

#算法思想：把非字母的内容转换为空格；遍历一下字符串把非字母的替换为空格

s="I am a good good baby! You too!"

word_list=s.split() #调试

print(word_list)#调试

new_s=""#作用把切割的单词放进这个字符串，因为字符串无法修改只能拼接

for i in s:

    if (i>='a' and i<='z') or (i>='A' and i<='Z'):

        new_s+=i

    else:

        new_s+=""

print(new_s)#调试

print(new_s.split())#调试

print(len(new_s.split()))

#以上封装函数：

def count_word_list(s):

    if not isinstance(s,str):

        return None

    word_list=s.split()

    print(word_list)  #调试

    new_s=""

    for i in s:

        if (i>='a' and i<='z') or (i>='A' and i<='Z'):

            new_s+=i

        else:

            new_s+=" "

    return len(new_s.split())

sentence="I am a good good baby! You too!"

print(count_word_list(sentence))