**这是本文档旧的修订版！**
字符串
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:] | fg | 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 |