Python Print Error Stream
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Print Sys.stderr Comments
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Print Sys.stderr Comments In Python
Join them; it only takes a minute: Sign 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, python redirect 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 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 standard error stream function in python 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:
Post #1 of 2 (23257 views) Permalink Simple print to stderr By default the print statement sends to stdout I want to send to
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stderr Try print "my meeage", file=sys.stderr I got > SyntaxError: invalid syntax print(input()) I try print "my message", sys.stderr But it still sent to stdout. What is the syntax? I wouldn't
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understand Python's manual > print([object, ...][, sep=' '][, end='n'][, file=sys.stdout])¶ > > Print object(s) to the stream file, separated by sep and followed by end. sep, end and file, if present, http://stackoverflow.com/questions/5574702/how-to-print-to-stderr-in-python must be given as keyword arguments. > > All non-keyword arguments are converted to strings like str() does and written to the stream, separated by sep and followed by end. Both sep and end must be strings; they can also be None, which means to use the default values. If no object is given, print() will just write end. > > The http://www.gossamer-threads.com/lists/python/python/689509 file argument must be an object with a write(string) method; if it is not present or None, sys.stdout will be used. -- http://mail.python.org/mailman/listinfo/python-list mnordhoff at mattnordhoff Oct27,2008,11:41AM Post #2 of 2 (22979 views) Permalink Re: Simple print to stderr [In reply to] RC wrote: > By default the print statement sends to stdout > I want to send to stderr > > Try > > print "my meeage", file=sys.stderr > > I got >> SyntaxError: invalid syntax > > I try > > print "my message", sys.stderr > > But it still sent to stdout. > What is the syntax? > > I wouldn't understand Python's manual
2.6. Python 3.0, also known as "Python 3000" or "Py3K", is the first ever intentionally backwards incompatible Python release. There are more changes than in a typical release, and more that are important for https://docs.python.org/3/whatsnew/3.0.html all Python users. Nevertheless, after digesting the changes, you'll find that Python really hasn't changed all that much - by and large, we're mostly fixing well-known annoyances and warts, and removing a lot of old cruft. This article doesn't attempt to provide a complete specification of all new features, but instead tries to give a convenient overview. For full details, you should refer to the documentation for Python 3.0, and/or the many in python PEPs referenced in the text. If you want to understand the complete implementation and design rationale for a particular feature, PEPs usually have more details than the regular documentation; but note that PEPs usually are not kept up-to-date once a feature has been fully implemented. Due to time constraints this document is not as complete as it should have been. As always for a new release, the Misc/NEWS file in print sys.stderr comments the source distribution contains a wealth of detailed information about every small thing that was changed. Common Stumbling Blocks¶ This section lists those few changes that are most likely to trip you up if you're used to Python 2.5. Print Is A Function¶ The print statement has been replaced with a print() function, with keyword arguments to replace most of the special syntax of the old print statement (PEP 3105). Examples: Old: print "The answer is", 2*2 New: print("The answer is", 2*2) Old: print x, # Trailing comma suppresses newline New: print(x, end=" ") # Appends a space instead of a newline Old: print # Prints a newline New: print() # You must call the function! Old: print >>sys.stderr, "fatal error" New: print("fatal error", file=sys.stderr) Old: print (x, y) # prints repr((x, y)) New: print((x, y)) # Not the same as print(x, y)! You can also customize the separator between items, e.g.: print("There are <", 2**32, "> possibilities!", sep="") which produces: There are <4294967296> possibilities! Note: The print() function doesn't support the "softspace" feature of the old print statement. For example, in Python 2.x, print "A\n", "B" would write "A\nB\n"; but in Python 3.0, print("A\n", "B") writes "A\n B\n". Initially