Question

I would like to log all the output of a Python script. I tried:

import sys

log = []

class writer(object):
    def write(self, data):
        log.append(data)

sys.stdout = writer()
sys.stderr = writer()

Now, if I “print ‘something’ ” it gets logged. But if I make for instance some syntax error, say “print ‘something# “, it wont get logged – it will go into the console instead.

How do I capture also the errors from Python interpreter?

I saw a possible solution here:

http://www.velocityreviews.com/forums/showpost.php?p=1868822&postcount=3

but the second example logs into /dev/null – this is not what I want. I would like to log it into a list like my example above or StringIO or such…

Also, preferably I don’t want to create a subprocess (and read its stdout and stderr in separate thread).

Answer 1

You can’t do anything in Python code that can capture errors during the compilation of that same code. How could it? If the compiler can’t finish compiling the code, it won’t run the code, so your redirection hasn’t even taken effect yet.

That’s where your (undesired) subprocess comes in. You can write Python code that redirects the stdout, then invokes the Python interpreter to compile some other piece of code.