# 字符串

用单引号`''` 或者 `""` 括起来的任意字符表示字符串

如果字符串中既包含`'` 也包含 `"`, 可以用转义字符来表示。

例如： `str="I'm \"tux\""`
## 字符串截取操作

`str='abcdefg'`

| syntax      | result   | description                                                   |
| `str[0] `   | a        | character in position 0                                       |
| `str[5] `   | f        | character in position 5                                       |
| `str[-1] `  | g        | the last character                                            |
| `str[-2] `  | f        | the second last character                                     |
| `str[0:2] ` | ab       | characters from position 0(include) to position 2(exclude)    |
| `str[2:5] ` | cde      | characters from position 2(include) to position 5(exclude)    |
| `str[:2] `  | ab       | characters from the beginning to position 2(exclude)          |
| `str[:-1]`  | abcdef   | characters from the beginning the the last character(exclude) |
| `str[4:] `  | efg      | characters from position 4 to the end                         |
| `str[-2:] ` | fg       | characters from the second last to the end                    |
| `str[-1:] ` | f        | the last character                                            |
| `str[:]`    | abcdefg  | all the characters                                            |
| `str[::-1]` | gfedcba  | `[::-1]` 字符串最后一个字符到第一个字符，也就是对字符串逆序   |
| `str[::-2]` | geca     | `[::-2]` 字符串逆序，间隔一个字符                             |

## ord & chr

ord将字符转换为对应的ASCII码

chr 将0-255的任一整数转换为对应的字符

##  join

string.join(iterable)

将多个字符串连接, join的参数必须是可迭代的对象，例如 list

例：

```
str1 = 'Hello'
str2 = 'Tux'
'.'.join([str1, str2])
```

结果为:  Hello.Tux

```
'-'.join(str1, str2)
```

结果为:  Hello-Tux

字符串的链接符号即调用join的字符串