字符串练习题

>>> s="I am a boy!"
>>> s.split()
[‘I‘, ‘am‘, ‘a‘, ‘boy!‘]
>>> word_list = s.split()
>>> result = 0
>>> for i in word_list:
...     if "a" not in i:
...         result +=1
...
>>> result
2

>>> s="I am a boy!"
>>> result =""
>>> for i in range(len(s)):
...     print(i)
...     if i%2==0:
...         if (s[i]>="a" and s[i]<="z") or (s[i]>="A" and s[i]<="Z"):
...             result =result+s[i]+"*"
...
0
1
2
3
4
5
6
7
8
9
10
>>> print(result)
I*a*o*
>>>

>>> s="abcdefg"
>>> s[0]+s[-1]
‘ag‘

>>> s[:1]+s[-1]
‘ag‘

>>> s[:2]+s[:-3:-1]
‘abgf‘

>>> s[:2]+s[-2:]
‘abfg‘