An example for setting up logging using Python's StdLib.
To use the yaml configuration file you will need to install ruamel.yaml.
pip install ruamel.yamlexample_simple.pycontains a lot of explanatory comments. Make sure you read it.example_multi.pyshowcases what happens when you spawn multiple processes/threads
If you run python3 simple_example.py as it is, you will get the following output:
INFO:root:This is the logger configured by `logging.basicConfig()`. INFO:root:We will disable this logger when we setup logger using the config file. INFO:root:This logger can be useful if we e.g. want to log the path of the config file INFO:root:we will be using which we can get e.g. as a command line argument etc. INFO:root: INFO:root:config file: log_config.yml 2019-07-12 18:00:51,099; INFO ; [19123 - 139698662942528]; root ; <module> 78: This is the logger configured by `logging.config.dictConfig()`. 2019-07-12 18:00:51,099; INFO ; [19123 - 139698662942528]; root ; main ; 44: This is an INFO message on the root logger. 2019-07-12 18:00:51,099; WARNING ; [19123 - 139698662942528]; child ; main ; 48: This is a WARNING message on the child logger. 2019-07-12 18:00:51,099; ERROR ; [19123 - 139698662942528]; child ; main ; 51: This is an ERROR message. --- Logging error --- Traceback (most recent call last): File "/usr/lib/python3.6/logging/handlers.py", line 1010, in emit smtp = smtplib.SMTP(self.mailhost, port, timeout=self.timeout) File "/usr/lib/python3.6/smtplib.py", line 251, in __init__ (code, msg) = self.connect(host, port) File "/usr/lib/python3.6/smtplib.py", line 336, in connect self.sock = self._get_socket(host, port, self.timeout) File "/usr/lib/python3.6/smtplib.py", line 307, in _get_socket self.source_address) File "/usr/lib/python3.6/socket.py", line 724, in create_connection raise err File "/usr/lib/python3.6/socket.py", line 713, in create_connection sock.connect(sa) ConnectionRefusedError: [Errno 111] Connection refused Call stack: File "example_simple.py", line 80, in <module> main() File "example_simple.py", line 51, in main child.error("This is an ERROR message.") Message: 'This is an ERROR message.' Arguments: () 2019-07-12 18:00:51,122; DEBUG ; [19123 - 139698662942528]; mypkg ; <module> 5: Logging from mypkg! 2019-07-12 18:00:51,122; DEBUG ; [19123 - 139698662942528]; mypkg.subpkg1 ; <module> 5: Logging from subpkg1! 2019-07-12 18:00:51,122; DEBUG ; [19123 - 139698662942528]; mypkg.subpkg1.a ; func_a ; 7: Logging from a 2019-07-12 18:00:51,122; DEBUG ; [19123 - 139698662942528]; mypkg.subpkg1.b ; func_b ; 7: Logging from b 2019-07-12 18:00:51,123; DEBUG ; [19123 - 139698662942528]; mypkg.subpkg2 ; <module> 5: Logging from subpkg2! This traceback is not a related to our application. It has to do with the logging configuration. More specifically we have set an smtp handler that tries to send an email using a MailServer that runs on 127.0.0.1:60025, but there is no server listening to that ip/port. While developing, we can easily setup such a server by running the following command on a separate console session:
python3 -m smtpd -n -c DebuggingServer 127.0.0.1:60025Needless to say, on production we should set up a proper MailServer. Anyway, now, if we execute the script we will get the following output:
INFO:root:This is the logger configured by `logging.basicConfig()`. INFO:root:We will disable this logger when we setup logger using the config file. INFO:root:This logger can be useful if we e.g. want to log the path of the config file INFO:root:we will be using which we can get e.g. as a command line argument etc. INFO:root: INFO:root:config file: log_config.yml 2019-07-12 18:01:38,170; INFO ; [19540 - 140070813353792]; root ; <module> 78: This is the logger configured by `logging.config.dictConfig()`. 2019-07-12 18:01:38,170; INFO ; [19540 - 140070813353792]; root ; main ; 44: This is an INFO message on the root logger. 2019-07-12 18:01:38,170; WARNING ; [19540 - 140070813353792]; child ; main ; 48: This is a WARNING message on the child logger. 2019-07-12 18:01:38,170; ERROR ; [19540 - 140070813353792]; child ; main ; 51: This is an ERROR message. 2019-07-12 18:01:38,233; DEBUG ; [19540 - 140070813353792]; mypkg ; <module> 5: Logging from mypkg! 2019-07-12 18:01:38,233; DEBUG ; [19540 - 140070813353792]; mypkg.subpkg1 ; <module> 5: Logging from subpkg1! 2019-07-12 18:01:38,234; DEBUG ; [19540 - 140070813353792]; mypkg.subpkg1.a ; func_a ; 7: Logging from a 2019-07-12 18:01:38,234; DEBUG ; [19540 - 140070813353792]; mypkg.subpkg1.b ; func_b ; 7: Logging from b 2019-07-12 18:01:38,234; DEBUG ; [19540 - 140070813353792]; mypkg.subpkg2 ; <module> 5: Logging from subpkg2! While, on the console that runs the Mail Server we will get the following output:
---------- MESSAGE FOLLOWS ---------- b'From: [email protected]' b'To: [email protected]' b'Subject: Something went wrong' b'Date: Fri, 12 Jul 2019 18:01:38 +0200' b'Content-Type: text/plain; charset="utf-8"' b'Content-Transfer-Encoding: 7bit' b'MIME-Version: 1.0' b'X-Peer: 127.0.0.1' b'' b'Level: ERROR\\nTime: 2019-07-12 18:01:38,170\\nProcess: 19540\\nThread: 140070813353792\\nLogger: child\\nPath: example_simple:51\\nFunction :main\\nMessage: This is an ERROR message.\\n' ------------ END MESSAGE ------------