Python Print Error To Stderr
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Print Sys.stderr Comments In Python
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File=sys.stderr Invalid Syntax
up 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 zen of Python #13 †, so what's the preferred way to do it? Are there any advantages or disadvantages to python redirect stderr 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 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 print(input()) about Stack Overflow the company Business Learn more about hiring developers or posting ads print( hello world end= o ) in python with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow standard error stream function in python is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up stderr.write; printing strings up vote 3 down vote favorite 1 I am http://stackoverflow.com/questions/5574702/how-to-print-to-stderr-in-python new to Python and having some trouble with the stderr.write function. I will try to illustrate it with code. Before I was doing this: print "Unexpected error! File {0} could not be converted." .format(src) But then I wanted to separate the error messages from other status messages so I tried doing this: sys.stderr.write "Unexpected error! File %s could not be converted." src But this results in error. I googled it http://stackoverflow.com/questions/6663778/stderr-write-printing-strings as well but i couldn't find anything. Could anyone please help me out here. How can I print the string src using stderr.write? python stderr share|improve this question edited Jun 5 '12 at 23:21 user212218 asked Jul 12 '11 at 11:57 HasIq. 5014 add a comment| 4 Answers 4 active oldest votes up vote 7 down vote accepted In Python 2.x: sys.stderr.write("Unexpected error! File %s could not be converted." % src) Or, in Python 2.x and 3.x: sys.stderr.write("Unexpected error! File {0} could not be converted.".format(src)) share|improve this answer answered Jul 12 '11 at 11:59 mrbox 47329 Also, consider using the logging module to log. –Noufal Ibrahim Jul 12 '11 at 12:04 1 Of course logging is very usefull- but sometimes I it is better to log more details and print to stderr something different to mark that an error happened –mrbox Jul 12 '11 at 12:08 Thx! Works like a charm! :-) –HasIq. Jul 12 '11 at 12:08 add a comment| up vote 1 down vote Functions in Python need to be followed by parens ((...)), optionally containing arguments, in order to be invoked. sys.stderr.write("Unexpected error! File %s could not be converted.\n" % (src,)) share|improve this answer answered Jul 12 '11
concept of standard input, standard output, and standard error. This section is for the rest of you. Standard output and standard error (commonly abbreviated http://www.diveintopython.net/scripts_and_streams/stdin_stdout_stderr.html stdout and stderr) are pipes that are built into every UNIX system. When you print something, it goes to the stdout pipe; when your program crashes and prints out debugging information (like a traceback in Python), it goes to the stderr pipe. Both of these pipes are ordinarily just connected to the terminal window where you are working, so in python when a program prints, you see the output, and when a program crashes, you see the debugging information. (If you're working on a system with a window-based Python IDE, stdout and stderr default to your "Interactive Window".) Example10.8.Introducing stdout and stderr >>> for i in range(3): ... print 'Dive in' Dive in Dive in Dive in >>> import sys >>> print sys.stderr comments for i in range(3): ... sys.stdout.write('Dive in') Dive inDive inDive in >>> for i in range(3): ... sys.stderr.write('Dive in') Dive inDive inDive in As you saw in Example6.9, "Simple Counters", you can use Python's built-in range function to build simple counter loops that repeat something a set number of times. stdout is a file-like object; calling its write function will print out whatever string you give it. In fact, this is what the print function really does; it adds a carriage return to the end of the string you're printing, and calls sys.stdout.write. In the simplest case, stdout and stderr send their output to the same place: the Python IDE (if you're in one), or the terminal (if you're running Python from the command line). Like stdout, stderr does not add carriage returns for you; if you want them, add them yourself. stdout and stderr are both file-like objects, like the ones you discussed in Section10.1, "Abstracting input sources", but they are both write-only. They have no read method, only write. Still, they are file-like ob