How to adjust the time string which is inserted when rotating?

[changchiyou]

The code below generate record.2023-06-25_21-37-48_944911.log after rotating The time string 2023-06-25_21-37-48_944911 is the time when the script has been launched.

from logger import logger

logger.remove()
logger.logger.add("record.log", rotation="00:00")

# do something

Is it possible to adjust the format of time string?

To be more specific, I want record.2023-06-25.log(record.{yesterday date time: YYYY-MM-DD}.log) would be generate on 2023-06-26 00:00, instead of record.2023-06-25_21-37-48_944911.log(record.{script launching time}.log).

---

I have read Logger.add but still have no idea about my question.

[Delgan]

Hi.

You can define a custom compression function to actually rename the file as desired:

def rename(filepath):
    today = datetime.datetime.now().strftime("%Y-%m-%d")
    os.rename(filepath, f"record.{today}.log")

logger.add("record.log", rotation="00:00", compression=rename)

[changchiyou]

@Delgan Thanks for your replay 👍

In order to avoid misunderstanding, I would like to ask detailed questions about your answer: Is the codes in your answer just a example about how to use compression parameter or that is the exact solution for my needs?

---

From my understanding in the codes you provied to me, rename convert the record.log to record.2023-06-26.log on 2023-06-26 00:00. But I thought record.2023-06-26.log should means "the record of logs happened in 2023-06-26".

def rename(filepath):
    today = datetime.datetime.now().strftime("%Y-%m-%d")
    os.rename(filepath, f"record.{today}.log")

logger.add("record.log", rotation="00:00", compression=rename)

Should I change the example you gave me to

def rename(filepath):
    today = (datetime.datetime.now() - datetime.timedelta(days=1)).strftime("%Y-%m-%d")
    os.rename(filepath, f"record.{today}.log")

logger.add("record.log", rotation="00:00", compression=rename)

or

def rename(filepath):
    today = datetime.datetime.now().strftime("%Y-%m-%d")
    os.rename(filepath, f"record.{today}.log")

logger.add("record.log", rotation="24:00", compression=rename)

for my own needs?

[Delgan]

Sorry, that was an oversight. I think you indeed need to remove datetime.timedelta(days=1) to get the desired result. 👍

[changchiyou]

Sorry, that was an oversight. I think you indeed need to remove datetime.timedelta(days=1) to get the desired result. 👍

You are right, the answer above you provide to me is correct.

---

and the code above(in my question) is incorrect:

• - datetime.timedelta(days=1) is needed to remove:

Should I change the example you gave me to

def rename(filepath):
    today = (datetime.datetime.now() - datetime.timedelta(days=1)).strftime("%Y-%m-%d")
    os.rename(filepath, f"record.{today}.log")

logger.add("record.log", rotation="00:00", compression=rename)

• rotation="24:00" would get a format error exception:

or

def rename(filepath):
    today = datetime.datetime.now().strftime("%Y-%m-%d")
    os.rename(filepath, f"record.{today}.log")

logger.add("record.log", rotation="24:00", compression=rename)

for my own needs?

[Delgan]

Be careful there might be a bug with rotation though: #894

[changchiyou]

It's not a bug report of loguru, just wanna share my mis-understanding of the answer above

---

I got another error and couldn't find out for days:

The answer code provided by @Delgan works perfectly

Hi.

You can define a custom compression function to actually rename the file as desired:

def rename(filepath):
    today = datetime.datetime.now().strftime("%Y-%m-%d")
    os.rename(filepath, f"record.{today}.log")

logger.add("record.log", rotation="00:00", compression=rename)

But I have not noticed that the input argument filepath is already renamed when rotating, instead of keeping origin file name. For example, If I set loguru.logger via logger.add("record.log", ...) the filepath would be like

/[abs_paht]/record.2023-07-06_08-56-33_328410.log

instead of (what I thought before)

/[abs_paht]/record..log

Therefore I got a serious bug when I tried to rename from filepath. 😢

[changchiyou]

@Delgan I found that the build-in solution in #894 :

from loguru import logger

logger.remove()
logger.add(
    'logs/log.{time:YYYY-MM-DD}.log',
    level='INFO',
    rotation="00:00",
    retention='1 months',
    enqueue=True
)

logger.info('hello world')
logger.info('hello world')

Which would you suggest, the answer above #899 (comment) or this build-in solution?

[Delgan]

@changchiyou It depends on your preferences.

Using the built-in solution the current logged file will contain the date, e.g. "record.2023-07-09.log", whereas with your solution, the current file will simply be "record.log".