I'm trying to find out a way in python to redirect the script execution log to a file as well as stdout in a pythonic way. Is there any easy way of achieving this?
8 Answers
import logging logger = logging.getLogger('scope.name') file_log_handler = logging.FileHandler('logfile.log') logger.addHandler(file_log_handler) stderr_log_handler = logging.StreamHandler() logger.addHandler(stderr_log_handler) # nice output format formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s') file_log_handler.setFormatter(formatter) stderr_log_handler.setFormatter(formatter) logger.info('Info message') logger.error('Error message') I came up with this [untested]
import sys class Tee(object): def __init__(self, *files): self.files = files def write(self, obj): for f in self.files: f.write(obj) f.flush() # If you want the output to be visible immediately def flush(self) : for f in self.files: f.flush() f = open('out.txt', 'w') original = sys.stdout sys.stdout = Tee(sys.stdout, f) print "test" # This will go to stdout and the file out.txt #use the original sys.stdout = original print "This won't appear on file" # Only on stdout f.close() print>>xyz in python will expect a write() function in xyz. You could use your own custom object which has this. Or else, you could also have sys.stdout refer to your object, in which case it will be tee-ed even without >>xyz.
I just want to build upon Serpens answer and add the line:
logger.setLevel('DEBUG') This will allow you to chose what level of message gets logged.
For example in Serpens example,
logger.info('Info message') Will not get recorded as it defaults to only recording Warnings and above.
More about levels used can be read about here
Probably the shortest solution:
def printLog(*args, **kwargs): print(*args, **kwargs) with open('output.out','a') as file: print(*args, **kwargs, file=file) printLog('hello world') Writes 'hello world' to sys.stdout and to output.out and works exactly the same way as print().
Note: Please do not specify the file argument for the printLog function. Calls like printLog('test',file='output2.out') are not supported.
You should use the logging library, which has this capability built in. You simply add handlers to a logger to determine where to send the output.
The easiest solution is to redirect the standard output. In your python program file use the following:
if __name__ == "__main__": sys.stdout = open('file.log', 'w') #sys.stdout = open('/dev/null', 'w') main() Any std output (e.g. the output of print 'hi there') will be redirected to file.log or if you uncomment the second line, any output will just be suppressed.
Here's a small improvement that to @UltraInstinct's Tee class, modified to be a context manager and also captures any exceptions.
import traceback import sys # Context manager that copies stdout and any exceptions to a log file class Tee(object): def __init__(self, filename): self.file = open(filename, 'w') self.stdout = sys.stdout def __enter__(self): sys.stdout = self def __exit__(self, exc_type, exc_value, tb): sys.stdout = self.stdout if exc_type is not None: self.file.write(traceback.format_exc()) self.file.close() def write(self, data): self.file.write(data) self.stdout.write(data) def flush(self): self.file.flush() self.stdout.flush() To use the context manager:
print("Print") with Tee('test.txt'): print("Print+Write") raise Exception("Test") print("Print") Create an output file and custom function:
outputFile = open('outputfile.log', 'w') def printing(text): print(text) if outputFile: outputFile.write(str(text)) Then instead of print(text) in your code, call printing function.
printing("START") printing(datetime.datetime.now()) printing("COMPLETE") printing(datetime.datetime.now()) 
