Python log output in a file

Question

I have a python function which prints some lines on terminal.

Here is how I execute the function:

python3 test.py

Here is some code from the file:

column1 = "|=========="
        column2 = "|==============================================================="
        column3 = "|==================================="
        column4 = "|======================="

        print("\n"+column1+column2+column3+column4+"|")
        print("|SCRIPT ID    |SCRIPT NAME                                                       |Start Time                         |RUN ID             |")
        print(column1+column2+column3+column4+"|")

It prints the following in terminal:

|==========|===============================================================|===================================|=======================|
|SCRIPT ID    |SCRIPT NAME                                                       |Start Time                         | RUN ID             |
|==========|===============================================================|===================================|=======================|
|1         |TEST_SCRIPT                                    |2020-04-17 11:46:28.054074+05:30   |201                    |
|==========|===============================================================|===================================|=======================|

Entering - SCRIPT
     Verification Started
     Verification Completed in 0 Hours 00 Min 00.000602 sec
     Methods Execution Started
     Methods Execution Completed
EXITING - SCRIPT

I want to maintain the output of the function in a log file. So, if I run python3 test.py, it should create a file called test.py-202004171148.log in a folder called as logs storing all the output in the file.

How can I do this?

do you want save test.py-202004171148.log with timestamp or just random numbers? — Bhupesh lad
– Bhupesh lad, Commented Apr 17, 2020 at 6:28
Is it possible to generate the file without writing filename.log every time? — dang
– dang, Commented Apr 17, 2020 at 6:28

satya · Accepted Answer · 2020-04-17 06:41:46Z

3

save file with datetime:

import datetime
file = open(str(datetime.now().strftime('test.py-%Y%m%d%H%M%S.log')), "w")
file.write("yourlogs")
file.close()

answered Apr 17, 2020 at 6:41

satya

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Comments

Bhupesh lad · Accepted Answer · 2020-04-17 06:34:26Z

1

to saving file you can use:

import datetime
file = open("test.py-"+str(datetime.datetime.now().timestamp())+".log", "w")
file.write("yourlogs")
file.close()

answered Apr 17, 2020 at 6:34

Bhupesh lad

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Comments

Rajarishi Devarajan · Accepted Answer · 2020-04-17 09:21:26Z

1

Adding these few lines of code to the top of your script should redirect all output to be printed to console AND ALSO written to a file

import sys
import datetime

class Printer(object):
    def __init__(self, *files):
        self.files = files
    def write(self, obj):
        for file in self.files:
            file.write(obj)
            file.flush()
    def flush(self):
        for file in self.files:
            file.flush()

f = open(f"{__file__}-{datetime.datetime.now().strftime('%Y%m%d%H%M%S')}.log", 'w')
sys.stdout = Printer(sys.stdout, f)

#Your print statements below
print("Hello world!")

edited Apr 17, 2020 at 9:21

answered Apr 17, 2020 at 6:37

Rajarishi Devarajan

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10 Comments

dang Over a year ago

Can we put the function name and put in the folder - logs

dang Over a year ago

Also, can I print on screen and also save to file

Rajarishi Devarajan Over a year ago

Yes, you can create a folder logs, and save all your output to it. I will edit my answer to reflect the same.

dang Over a year ago

Would be nice to get the filename dynamically. For example, if it is test.py-20200417.log or abc.py-20200427.log

Rajarishi Devarajan Over a year ago

You can access the filename in the variable __file__

|

kichik · Accepted Answer · 2020-04-17 06:29:53Z

0

You can use the logging module for that. You will have to replace print() with logging.info(), logging.warning(), or logging.error() depending on your desired log level.

import logging
from datetime import datetime
fn = datetime.now().strftime('logs/test.py-%Y%m%d%H%M%S.log')
logging.basicConfig(filename=fn, level=logging.INFO)
logging.info('Entering - SCRIPT')
logging.info('etc...')

The default format will prefix every message with the log level and logger name. If you don't want that, you can override it with format.

logging.basicConfig(filename=fn, level=logging.INFO, format='%(message)s')

answered Apr 17, 2020 at 6:29

kichik

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