Question or problem about Python programming:
How to write custom console log function to output only on the console window log messages on a single line (not append) until the first regular log record.
progress = ProgressConsoleHandler() console = logging.StreamHandler() logger = logging.getLogger('test') logger.setLevel(logging.DEBUG) logger.addHandler(console) logger.addHandler(progress) logger.info('test1') for i in range(3): logger.progress('remaining %d seconds' % i) time.sleep(1) logger.info('test2')
So that the console output is only three lines:
INFO: test1 remaining 0 seconds... INFO: test2
Any suggestions on the best way on how to implement this?
How to solve the problem:
import logging class ProgressConsoleHandler(logging.StreamHandler): """ A handler class which allows the cursor to stay on one line for selected messages """ on_same_line = False def emit(self, record): try: msg = self.format(record) stream = self.stream same_line = hasattr(record, 'same_line') if self.on_same_line and not same_line: stream.write(self.terminator) stream.write(msg) if same_line: stream.write('... ') self.on_same_line = True else: stream.write(self.terminator) self.on_same_line = False self.flush() except (KeyboardInterrupt, SystemExit): raise except: self.handleError(record) if __name__ == '__main__': import time progress = ProgressConsoleHandler() console = logging.StreamHandler() logger = logging.getLogger('test') logger.setLevel(logging.DEBUG) logger.addHandler(progress) logger.info('test1') for i in range(3): logger.info('remaining %d seconds', i, extra={'same_line':True}) time.sleep(1) logger.info('test2')
Notice that only one handler is being registered, and the extra
keyword argument to let the handler know it should stay on one line. There is more logic in the emit()
method to handle changes between messages that should stay on one line and messages that need to have their own line.