如何自定义Python日志的时间格式？

Question

我刚接触Python的日志记录功能，打算在我的项目中使用它。我想把时间格式调整得更符合我的喜好。这是我从一个教程里复制的简短代码：

import logging

# create logger
logger = logging.getLogger("logging_tryout2")
logger.setLevel(logging.DEBUG)

# create console handler and set level to debug
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)

# create formatter
formatter = logging.Formatter("%(asctime)s;%(levelname)s;%(message)s")

# add formatter to ch
ch.setFormatter(formatter)

# add ch to logger
logger.addHandler(ch)

# "application" code
logger.debug("debug message")
logger.info("info message")
logger.warn("warn message")
logger.error("error message")
logger.critical("critical message")

这是运行后的输出：

2010-07-10 10:46:28,811;DEBUG;debug message
2010-07-10 10:46:28,812;INFO;info message
2010-07-10 10:46:28,812;WARNING;warn message
2010-07-10 10:46:28,812;ERROR;error message
2010-07-10 10:46:28,813;CRITICAL;critical message

我想把时间格式缩短到只显示：'2010-07-10 10:46:28'，去掉毫秒的部分。我查看了Formatter.formatTime，但我有点困惑。

Answer 1

为了补充其他回答，这里有来自Python文档的变量列表。

Directive   Meaning Notes

%a  Locale’s abbreviated weekday name.   
%A  Locale’s full weekday name.  
%b  Locale’s abbreviated month name.     
%B  Locale’s full month name.    
%c  Locale’s appropriate date and time representation.   
%d  Day of the month as a decimal number [01,31].    
%H  Hour (24-hour clock) as a decimal number [00,23].    
%I  Hour (12-hour clock) as a decimal number [01,12].    
%j  Day of the year as a decimal number [001,366].   
%m  Month as a decimal number [01,12].   
%M  Minute as a decimal number [00,59].  
%p  Locale’s equivalent of either AM or PM. (1)
%S  Second as a decimal number [00,61]. (2)
%U  Week number of the year (Sunday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Sunday are considered to be in week 0.    (3)
%w  Weekday as a decimal number [0(Sunday),6].   
%W  Week number of the year (Monday as the first day of the week) as a decimal number [00,53]. All days in a new year preceding the first Monday are considered to be in week 0.    (3)
%x  Locale’s appropriate date representation.    
%X  Locale’s appropriate time representation.    
%y  Year without century as a decimal number [00,99].    
%Y  Year with century as a decimal number.   
%z  Time zone offset indicating a positive or negative time difference from UTC/GMT of the form +HHMM or -HHMM, where H represents decimal hour digits and M represents decimal minute digits [-23:59, +23:59].  
%Z  Time zone name (no characters if no time zone exists).   
%%  A literal '%' character.     

Answer 2

使用 logging.basicConfig，下面这个例子对我来说是有效的：

logging.basicConfig(
    filename='HISTORYlistener.log',
    level=logging.DEBUG,
    format='%(asctime)s.%(msecs)03d %(levelname)s %(module)s - %(funcName)s: %(message)s',
    datefmt='%Y-%m-%d %H:%M:%S',
)

这样你就可以在一行代码里设置格式和配置。生成的日志记录看起来像这样：

2014-05-26 12:22:52.376 CRITICAL historylistener - main: History log failed to start

Answer 3

在关于Formatter类的官方文档中提到：

这个构造函数有两个可选的参数：一个是消息格式字符串，另一个是日期格式字符串。

所以把

# create formatter
formatter = logging.Formatter("%(asctime)s;%(levelname)s;%(message)s")

改成

# create formatter
formatter = logging.Formatter("%(asctime)s;%(levelname)s;%(message)s",
                              "%Y-%m-%d %H:%M:%S")