Python logging: use milliseconds in time format

Question

By default logging.Formatter(\'%(asctime)s\') prints with the following format:

2011-06-09 10:54:40,638

where 638 is the milli

Answer 1

Please note Craig McDaniel's solution is clearly better.

---

logging.Formatter's formatTime method looks like this:

def formatTime(self, record, datefmt=None):
    ct = self.converter(record.created)
    if datefmt:
        s = time.strftime(datefmt, ct)
    else:
        t = time.strftime("%Y-%m-%d %H:%M:%S", ct)
        s = "%s,%03d" % (t, record.msecs)
    return s

Notice the comma in "%s,%03d". This can not be fixed by specifying a datefmt because ct is a time.struct_time and these objects do not record milliseconds.

If we change the definition of ct to make it a datetime object instead of a struct_time, then (at least with modern versions of Python) we can call ct.strftime and then we can use %f to format microseconds:

import logging
import datetime as dt

class MyFormatter(logging.Formatter):
    converter=dt.datetime.fromtimestamp
    def formatTime(self, record, datefmt=None):
        ct = self.converter(record.created)
        if datefmt:
            s = ct.strftime(datefmt)
        else:
            t = ct.strftime("%Y-%m-%d %H:%M:%S")
            s = "%s,%03d" % (t, record.msecs)
        return s

logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)

console = logging.StreamHandler()
logger.addHandler(console)

formatter = MyFormatter(fmt='%(asctime)s %(message)s',datefmt='%Y-%m-%d,%H:%M:%S.%f')
console.setFormatter(formatter)

logger.debug('Jackdaws love my big sphinx of quartz.')
# 2011-06-09,07:12:36.553554 Jackdaws love my big sphinx of quartz.

---

Or, to get milliseconds, change the comma to a decimal point, and omit the datefmt argument:

class MyFormatter(logging.Formatter):
    converter=dt.datetime.fromtimestamp
    def formatTime(self, record, datefmt=None):
        ct = self.converter(record.created)
        if datefmt:
            s = ct.strftime(datefmt)
        else:
            t = ct.strftime("%Y-%m-%d %H:%M:%S")
            s = "%s.%03d" % (t, record.msecs)
        return s

...
formatter = MyFormatter(fmt='%(asctime)s %(message)s')
...
logger.debug('Jackdaws love my big sphinx of quartz.')
# 2011-06-09 08:14:38.343 Jackdaws love my big sphinx of quartz.