上面的%Y等是时间格式，所以要想理解上面要表示个什么，先来看一下Python的时间格式.

• %a - abbreviated weekday name
• %A - full weekday name
• %b - abbreviated month name
• %B - full month name
• %c - preferred date and time representation
• %C - century number (the year pided by 100, range 00 to 99)
• %d - day of the month (01 to 31)
• %D - same as %m/%d/%y
• %e - day of the month (1 to 31)
• %g - like %G, but without the century
• %G - 4-digit year corresponding to the ISO week number (see %V).
• %h - same as %b
• %H - hour, using a 24-hour clock (00 to 23)
• %I - hour, using a 12-hour clock (01 to 12)
• %j - day of the year (001 to 366)
• %m - month (01 to 12)
• %M - minute
• %n - newline character
• %p - either am or pm according to the given time value
• %r - time in a.m. and p.m. notation
• %R - time in 24 hour notation
• %S - second
• %t - tab character
• %T - current time, equal to %H:%M:%S
• %u - weekday as a number (1 to 7), Monday=1. Warning: In Sun Solaris Sunday=1
• %U - week number of the current year, starting with the first Sunday as the first day of the first week
• %V - The ISO 8601 week number of the current year (01 to 53), where week 1 is the first week that has at least 4 days in the current year, and with Monday as the first day of the week
• %W - week number of the current year, starting with the first Monday as the first day of the first week
• %w - day of the week as a decimal, Sunday=0
• %x - preferred date representation without the time
• %X - preferred time representation without the date
• %y - year without a century (range 00 to 99)
• %Y - year including the century
• %Z or %z - time zone or name or abbreviation
• %% - a literal % character 
  我们的例子是以 年月日-时:分:秒 的形式显示日期的。 
  除此之外，还要理解%(asctime)s等格式符所代表的意义，%(asctime)s表示这个位置上是字符串形式的当前时间；%(levelname)s，如果是logger.debug则它是DEBUG，如果是logger.error则它是ERROR；%(message)s，假如有logger.warning("HAHA")，则在%(message)s位置上是字符串HAHA。更详细的格式符如下： 

  %(name)s	Logger的名字
  %(levelno)s	数字形式的日志级别
  %(levelname)s	文本形式的日志级别
  %(pathname)s	调用日志输出函数的模块的完整路径名，可能没有
  %(filename)s	调用日志输出函数的模块的文件名
  %(module)s	调用日志输出函数的模块名
  %(funcName)s	调用日志输出函数的函数名
  %(lineno)d	调用日志输出函数的语句所在的代码行
  %(created)f	当前时间，用UNIX标准的表示时间的浮 点数表示
  %(relativeCreated)d	输出日志信息时的，自Logger创建以 来的毫秒数
  %(asctime)s	字符串形式的当前时间。默认格式是 “2003-07-08 16:49:45,896”。逗号后面的是毫秒
  %(thread)d	线程ID。可能没有
  %(threadName)s	线程名。可能没有
  %(process)d	进程ID。可能没有
  %(message)s	用户输出的消息