Python——字符串

字符串定义

In [15]: q = “qqq”

In [16]: w = ‘www’

In [17]: e = ”’
….: eee
….: ”’

In [18]: type(q)
Out[18]: str

In [19]: type(w)
Out[19]: str

In [20]: type(e)
Out[20]: str

转义
\t #代表tab键
\n #代表换行
\’ #代表单引号
\” #代表双引号

字符串的特性
索引
In [21]: a = ‘hello’

In [22]: a[0]
Out[22]: ‘h’

In [23]: a[-1]
Out[23]: ‘o’

切片
In [24]: b = ‘hello word’

In [25]: b
Out[25]: ‘hello word’

In [26]: b[:]
Out[26]: ‘hello word’

In [27]: b[0:6]
Out[27]: ‘hello ‘

In [28]: b[0:6:1]
Out[28]: ‘hello ’
In [91]: b[0:6:2]
Out[91]: ‘hlo’

成员操作符
In [29]: a
Out[29]: ‘hello’

In [30]: ‘o’ in a
Out[30]: True

In [31]: ‘o’ not in a
Out[31]: False

连接操作符
In [35]: a + b
Out[35]: ‘hellohello word’

重复操作符
In [32]: “*”*10
Out[32]: ‘****’

In [33]: i = “*”*10

In [34]: print i + “哈哈” + i
**哈哈**

In [36]: print “哈哈”.center(30, “*”)
**哈哈**

In [11]: a.ljust(30, ‘*’)
Out[11]: ‘hello*********************’

In [12]: a.rjust(30, ‘*’)
Out[12]: ‘*********************hello’

结尾字符
In [1]: s = ‘hello’

In [2]: s
Out[2]: ‘hello’

In [3]: s.endswith(‘o’)
Out[3]: True

In [4]: s.endswith(‘o’,0,4)
Out[4]: False

In [5]: s.endswith(‘e’,0,4)
Out[5]: False

In [6]: s.endswith(‘l’,0,4)
Out[6]: True

开头字符
In [7]: s.startswith(‘h’)
Out[7]: True

In [8]: s.startswith(‘he’)
Out[8]: True

查找
In [9]: s = ‘hellow word’

In [10]: s
Out[10]: ‘hellow word’

In [11]: s.find(‘o’)
Out[11]: 4

In [12]: s.find(‘o’,5)
Out[12]: 8

替换
In [13]: s.replace(‘o’,’e’)
Out[13]: ‘hellew werd’

In [14]: s.replace(‘o’,’e’,1)
Out[14]: ‘hellew word’

删除
In [15]: s = ’ hello ‘

In [16]: s.strip()
Out[16]: ‘hello’

In [17]: s.lstrip()
Out[17]: ‘hello ‘

In [18]: s.rstrip()
Out[18]: ’ hello’

In [9]: s = “h e l l o”

In [10]: s.replace(” “, “”)
Out[10]: ‘hello’

一种应用
In [5]: input = raw_input(“input:”)#输入” 1”
input: 1

In [6]: ‘1’ == input #判断是否等于”1”
Out[6]: False

In [7]: input = raw_input(“input:”).strip() #去掉输入进去字符串的空格
input: 1

In [8]: ‘1’ == input #再次判断
Out[8]: True

In [1]: info = “wes fa w2 f”

In [2]: info.spli
info.split info.splitlines

In [2]: info.split() #将字符串分开后以列表的方式输出
Out[2]: [‘wes’, ‘fa’, ‘w2’, ‘f’]

比较
In [3]: cmp(“h”,”w”)
Out[3]: -1

In [4]: cmp(“h”,”a”)
Out[4]: 1

In [5]: cmp(“3”,”2”)
Out[5]: 1

In [6]: max(‘1234’)
Out[6]: ‘4’

In [7]: min(‘1234’)
Out[7]: ‘1’

枚举
In [1]: s = “hello”

In [2]: for i,j in enumerate(s): #将字符串以及它的索引值同时输出
…: print i,j
…:
0 h
1 e
2 l
3 l
4 o

zip
In [3]: q = “qwer”

In [4]: w = “QWER”

In [5]: e = “123”

In [6]: zip(q,w,e)
Out[6]: [(‘q’, ‘Q’, ‘1’), (‘w’, ‘W’, ‘2’), (‘e’, ‘E’, ‘3’)]

显示小数
In [1]: print “you money: %f” %(100000.88888888)
you money: 100000.888889

In [2]: print “you money: %.2f” %(100000.88888888)
you money: 100000.89

字符连接
In [8]: ” “.join(“hello”)
Out[8]: ‘h e l l o’

In [9]: ” “.join([“ni”, “hao”])
Out[9]: ‘ni hao’

In [10]: “\n”.join([“ni”, “hao”])
Out[10]: ‘ni\nhao’

In [11]: print “\n”.join([“ni”, “hao”])
ni
hao

L.count()
查看某个字符出现了几次

L.insert(0.’ftp’)
往索引处加

L.reverse()
反转

L.sort()
排序，默认从小到大