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This tutorial shows how to write logs to files and stdout in Python.

logging.basicConfig()Log in to thestdout

If we want to print the logs to the console window and write the logs to a file, we can use logging.basicConfig()the log_log function to accomplish this process. logging.basicConfig()The log_log function configures some basic parameters for logging in Python. We can use streamthe log_log parameter of this function to specify that we also want to print this log on the console window. The rest of the configuration logging.basicConfig()is the same as using the log_log function to write the logs to a file. The following code demonstrates how we can write logs to the console window.

import logging
import sys

# Creating and Configuring Logger

Log_Format = "%(levelname)s %(asctime)s - %(message)s"

logging.basicConfig(
    filename="logfile.log",
    stream=sys.stdout,
    filemode="w",
    format=Log_Format,
    level=logging.ERROR,
)

logger = logging.getLogger()

# Testing our Logger

logger.error("Our First Error Message")

Output:

2021-06-13 05:15:24,093 - root - ERROR - Our First Error Message

logging.StreamHandler()Log in to thestdout

We can also logging.StreamHandler()write logs to the console window in Python using the logger function. By passing sys.stdoutto logging.StreamHandler()the logger function, we can create a stream handler that can print log messages to the console window. We can then addHandler()add this stream handler to our logger object using the logger function. The following code snippet shows us how to use logging.StreamHandler()the logger function to print log messages to the console window.

import logging
import sys

logger = logging.getLogger()
fileHandler = logging.FileHandler("logfile.log")
streamHandler = logging.StreamHandler(sys.stdout)
formatter = logging.Formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s")
streamHandler.setFormatter(formatter)
fileHandler.setFormatter(formatter)
logger.addHandler(streamHandler)
logger.addHandler(fileHandler)
logger.error("This is the first error")

Output:

2021-06-13 05:03:37,510 - root - ERROR - This is the first error

In the code above, we use the logging.FileHandler()and logging.StreamHandler()functions to write log messages This is the first errorto a file logfile.logand the console window. We first created a logger object, which we will use logging.getLogger()to write logs using the function. Then, we created a file handler fileHandlerand assigned it logging.FileHandler('logfile.log').

After that, we created a stream handler streamHandlerand assigned logging.StreamHandler(sys.stdout). After that, we created a formatter to logging.Formatter()format our output using the function and set the formatter setFormatter()for fileHandlerand streamHandlerusing the function. Following the previous step, we addHandler()added two new handlers to our logger object using the function. Finally, we used to logger.error('This is the first error')write error messages to our file and console window.