Python Write To Error Stream
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Print Sys.stderr Comments In Python
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Python Eprint
How to print to stderr in Python? up vote 676 down vote favorite 103 I've come across at least three ways to print to stderr: import sys print >> sys.stderr, 'spam' sys.stderr.write('spam\n') from __future__ import print_function print('spam', file=sys.stderr) It seems to contradict
Python Redirect Stderr
zen of Python #13 †, so what's the preferred way to do it? Are there any advantages or disadvantages to one way or the other? † There should be one — and preferably only one — obvious way to do it. python printing stderr zen share|improve this question edited Jun 21 '15 at 22:27 Peter Mortensen 10.3k1369107 asked Apr 7 '11 at 0:59 wim 77k24152241 27 The first way listed is one of the many things removed in Python 3. The consensus seems file=sys.stderr invalid syntax to be that the >> syntax was ugly anyway, and since print is now a function, the syntax would never work. –Steve Howard Aug 5 '11 at 21:50 14 Here's another one to add to your list: os.write(2, "spam\n") –Will Hardy Jul 10 '13 at 10:54 4 I use: sys.exit('Error:
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more standard error stream function in python about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users print( hello world end= o ) in python Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping print(input()) each other. Join them; it only takes a minute: Sign up How to redirect stderr in Python? up vote 12 down vote favorite 3 I would like to log all the output of a Python script. I tried: http://stackoverflow.com/questions/5574702/how-to-print-to-stderr-in-python 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 http://stackoverflow.com/questions/1956142/how-to-redirect-stderr-in-python 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). python redirect stderr share|improve this question asked Dec 24 '09 at 0:46 EcirH 108118 Perhaps writer should implement writelines() as well. Do not forget sys.stderr.flush() –Hamish Grubijan Dec 24 '09 at 0:54 add a comment| 4 Answers 4 active oldest votes up vote 4 down vote accepted 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. share|improve this answer answered Dec 24 '09 at 0:53 Ned Batchelder 180k31346497 You are right, of course it can't do it. Sorry for the stupid question. Another solution would be to "exec" the script inside another script. –EcirH Dec 24 '09 at 0:56 Not all code is compiled at once. import statements are one example. –user227667 Dec 24 '09 at 1:11 1 Another use cas
that happen when some software runs. The software's developer adds logging calls to their code to indicate that certain events have occurred. An event is described by https://docs.python.org/2/howto/logging.html a descriptive message which can optionally contain variable data (i.e. data that is potentially different for each occurrence of the event). Events also have an importance which the developer ascribes to the event; the importance can also be called the level or severity. When to use logging¶ Logging provides a set of convenience functions for simple logging usage. These are debug(), info(), warning(), error() and critical(). To determine when to use logging, see the table below, which states, for each of a set of common tasks, the best tool to use for it. Task you want to perform The best tool for the task Display console output for ordinary usage of a command line script or program print() Report events that occur during normal operation of a program (e.g. for status monitoring or fault investigation) logging.info() (or logging.debug() for very detailed output for diagnostic purposes) Issue a warning regarding a particular runtime event warnings.warn() in library code if the issue is avoidable and the client application should be modified to eliminate the warning logging.warning() if there is nothing the client application can do about the situation, but the event should still be noted Report an error regarding a particular runtime event Raise an exception Report suppression of an error without raising an exception (e.g. error handler in a long-running server process) logging.error(), logging.exception() or logging.critical() as appropriate for the specific error and application domain The logging functions are named after the level or severity of the events they are used to track. The standard levels and their applicability are described below (in increasing order of severity): Level When it's used DEBUG Detailed information, typically of interest only when diagnosing problems. INFO Confirmation that things are working as expected. WARNI