实时处理增量日志最佳实践
主要使用f.seek()和f.tell()实现
字符串处理函数：
s.find(substr, start, end) 查找子字符串，找不到则返回-1，找到则返回对应的索引
s.rfind(substr, start, end) 从右侧开始查找子字符串，找不到则返回-1; 找到则返回对应的索引；返回的结果和find一样，
s.index(substr, start, end) 查找返回子字符串的索引，找不到则报错,报错内容时substring not found
s.rindex(substr, start, end) 从右侧开始查找子字符串，找不到则报错；返回的结果和index一样
s.count(substr, start, end) 统计子字符串出现的次数
s.capitalize() 首字母大写
s.upper() 字符串转大写
s.lower() 字符串转小些
s.swapcase() 字符串大小写互转，大写则转小些，小些则转大写
s.split() 字符串分割变成列表
s.join(list) 使用字符串分割拼接列表
s.startswith(substr) 判断是否以子字符串开头
s.endswith(substr) 判断是否以子字符串结尾
len(str) 字符串的长度
cmp(str1, str2) 比较两个字符串
示例代码如下：
>>> s = "abcdefghijklmn"
>>> s.find("cd")
2
>>> s.rfind("cd")
2
>>> s.find("cd", 4, 9)
-1
>>> s.index("cd")
2
>>> s.index("cd", 4, 9)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: substring not found
>>> s.count("cd")
1
>>> s.count("cd", 4.)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: slice indices must be integers or None or have an __index__ method
>>> s.count("cd", 4, 9)
0
>>> s.capitalise()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'str' object has no attribute 'capitalise'
>>> s.capitalize()
'Abcdefghijklmn'
>>> s.upper()
'ABCDEFGHIJKLMN'
>>> s.lower()
'abcdefghijklmn'
>>> s.swapcase()
'ABCDEFGHIJKLMN'
>>> s.split()
['abcdefghijklmn']
>>> s.split("")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: empty separator
>>> s.split()
['abcdefghijklmn']
>>>
>>> list = [str(i) for i in range(9)]
>>> list
[']
>>> "==".join(list)
'0==1==2==3==4==5==6==7==8'