如何在不更改python代码的情况下将“print”命令输出重定向到文件？

Question

I want to redirect all the output of my django (1.10.4) app to a file

Firstly, I tried:

python manage.py runserver 0.0.0.0:8000 >test.log 2>&1

But it doesn't redirect the output of the print command.

For example, in my code there is a statement:

print ('query_content:')

using command:

python manage.py runserver 0.0.0.0:8000

I can see that 'query_content:' is printed out on the screen.

But with :

python manage.py runserver 0.0.0.0:8000 >test.log 2>&1

In the test.log, there are only something like this:

[05/Nov/2017 20:38:20] "GET ... HTTP/1.1" 200 22404
[05/Nov/2017 20:38:26] "POST ... HTTP/1.1" 200 13
[05/Nov/2017 20:38:26] "GET .... HTTP/1.1" 200 16800
[05/Nov/2017 20:38:30] "GET ... 200 22430
...

One solution is:

import sys
sys.stdout = open('file', 'w')
print 'test'

But sometimes it is impossible to change the python code, is there any solution?

update:

I found that if the log file already exists, then everything is fine. But if I specify a new file name, then the output of python "print ..." statement cannot save the log file.

Answer 1

我认为这个shell命令可能会输出结果。

python manage.py runserver 0.0.0.0:8000 2>&1 | tee file.txt

Answer 2

I believe that > writes to the file test.log whatever gets logged to console from Django.
print('query_content:') is not getting logged, therefore is not part of Django output.

You need to create a logger for your application:

1. In settings.py add:

    LOGGING = { 'version': 1, 'disable_existing_loggers': True, 'formatters': { 'standard': { 'format' : "[%(asctime)s] %(levelname)s [%(name)s:%(lineno)s] %(message)s", 'datefmt' : "%d/%b/%Y %H:%M:%S" }, }, 'handlers': { # This logs to the console 'console':{ 'level':'INFO', 'class':'logging.StreamHandler', 'formatter': 'standard' }, }, 'loggers': { 'django': { 'handlers':['console'], 'propagate': True, 'level':'INFO', }, }, 

2. Add the following were you want to log something:

    import logging mylogger = logging.getLogger(__name__) ... logger.info('query content: {}'.format(your_query_content)) ... 

---

Although the above solves your immediate problem, you can take it a step further:

Add a file handler in your LOGGER configuration:

1. On handlers add:

    'file': { 'class': 'logging.FileHandler', 'filename': 'a/file/location/logs.log', 'formatter': 'standard' }, 

2. On loggers.django update the handlers:

    'handlers':['console', 'file'], 

---

You can customize the above even further, but that is another subject:

More info on python and django logging:

1. https://docs.python.org/3/library/logging.html
2. https://docs.djangoproject.com/en/2.0/topics/logging/

Answer 3

TL;DR: if you have a loop in the end of a file you are feeding to manage.py shell add two newlines in the end.

In my case the reason print s were not present in the stdout was because they were never really executed in the first place. They were in a for loop that was at the end of file without two newlines or a newline and any other line (with a comment) after it. This way the shell was left waiting for a for loop code to be finished and it never was.