How to output to stderr

sys.stderr The purpose is to return error information

For example:

shutddown will prompt an error in red font.

>>> shutddown
Traceback (most recent call last):
  File "", line 1, in
    shutddown
NameError: name 'shutddown' is not defined

You can think about it, when we customize a function and then need to prompt the user for an error, but obviously it prints out in green font, then sys.stderr comes into play.

>>> import sys
>>> print 'closing...'
closing...
>>> print >> sys.stderr,'closing...'
closing...
>>> def test(x):
if x == 0: print >> sys.stderr,'Error--> x:can\'t is zero'
else:print x
>>> test('what\'s')
what's
>>> test(0)
Error--> x:can't is zero
>>>

or as follows:

>>> sys.stderr.write('sf')
sf
>>> print sys.stderr.write('sf')
sfNone

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