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# -*- coding: utf-8 -*-
"""Class to trap stdout and stderr and log them separately.
"""
#*****************************************************************************
# Copyright (C) 2001-2004 Fernando Perez <fperez@colorado.edu>
#
# Distributed under the terms of the BSD License. The full license is in
# the file COPYING, distributed as part of this software.
#*****************************************************************************
import exceptions
import sys
from cStringIO import StringIO
class OutputTrapError(exceptions.Exception):
"""Exception for OutputTrap class."""
def __init__(self,args=None):
exceptions.Exception.__init__(self)
self.args = args
class OutputTrap:
"""Class to trap standard output and standard error. They get logged in
StringIO objects which are available as <instance>.out and
<instance>.err. The class also offers summary methods which format this
data a bit.
A word of caution: because it blocks messages, using this class can make
debugging very tricky. If you are having bizarre problems silently, try
turning your output traps off for a while. You can call the constructor
with the parameter debug=1 for these cases. This turns actual trapping
off, but you can keep the rest of your code unchanged (this has already
been a life saver).
Example:
# config: trapper with a line of dots as log separator (final '\\n' needed)
config = OutputTrap('Config','Out ','Err ','.'*80+'\\n')
# start trapping output
config.trap_all()
# now all output is logged ...
# do stuff...
# output back to normal:
config.release_all()
# print all that got logged:
print config.summary()
# print individual raw data:
print config.out.getvalue()
print config.err.getvalue()
"""
def __init__(self,name='Generic Output Trap',
out_head='Standard Output. ',err_head='Standard Error. ',
sum_sep='\n',debug=0,trap_out=0,trap_err=0,
quiet_out=0,quiet_err=0):
self.name = name
self.out_head = out_head
self.err_head = err_head
self.sum_sep = sum_sep
self.out = StringIO()
self.err = StringIO()
self.out_save = None
self.err_save = None
self.debug = debug
self.quiet_out = quiet_out
self.quiet_err = quiet_err
if trap_out:
self.trap_out()
if trap_err:
self.trap_err()
def trap_out(self):
"""Trap and log stdout."""
if sys.stdout is self.out:
raise OutputTrapError,'You are already trapping stdout.'
if not self.debug:
self._out_save = sys.stdout
sys.stdout = self.out
def release_out(self):
"""Release stdout."""
if not self.debug:
if not sys.stdout is self.out:
raise OutputTrapError,'You are not trapping stdout.'
sys.stdout = self._out_save
self.out_save = None
def summary_out(self):
"""Return as a string the log from stdout."""
out = self.out.getvalue()
if out:
if self.quiet_out:
return out
else:
return self.out_head + 'Log by '+ self.name + ':\n' + out
else:
return ''
def flush_out(self):
"""Flush the stdout log. All data held in the log is lost."""
self.out.close()
self.out = StringIO()
def trap_err(self):
"""Trap and log stderr."""
if sys.stderr is self.err:
raise OutputTrapError,'You are already trapping stderr.'
if not self.debug:
self._err_save = sys.stderr
sys.stderr = self.err
def release_err(self):
"""Release stderr."""
if not self.debug:
if not sys.stderr is self.err:
raise OutputTrapError,'You are not trapping stderr.'
sys.stderr = self._err_save
self.err_save = None
def summary_err(self):
"""Return as a string the log from stderr."""
err = self.err.getvalue()
if err:
if self.quiet_err:
return err
else:
return self.err_head + 'Log by '+ self.name + ':\n' + err
else:
return ''
def flush_err(self):
"""Flush the stdout log. All data held in the log is lost."""
self.err.close()
self.err = StringIO()
def trap_all(self):
"""Trap and log both stdout and stderr.
Cacthes and discards OutputTrapError exceptions raised."""
try:
self.trap_out()
except OutputTrapError:
pass
try:
self.trap_err()
except OutputTrapError:
pass
def release_all(self):
"""Release both stdout and stderr.
Cacthes and discards OutputTrapError exceptions raised."""
try:
self.release_out()
except OutputTrapError:
pass
try:
self.release_err()
except OutputTrapError:
pass
def summary_all(self):
"""Return as a string the log from stdout and stderr, prepending a separator
to each (defined in __init__ as sum_sep)."""
sum = ''
sout = self.summary_out()
if sout:
sum += self.sum_sep + sout
serr = self.summary_err()
if serr:
sum += '\n'+self.sum_sep + serr
return sum
def flush_all(self):
"""Flush stdout and stderr"""
self.flush_out()
self.flush_err()
# a few shorthands
trap = trap_all
release = release_all
summary = summary_all
flush = flush_all
# end OutputTrap
#****************************************************************************
# Module testing. Incomplete, I'm lazy...
def _test_all():
"""Module testing functions, activated when the module is called as a
script (not imported)."""
# Put tests for this module in here.
# Define them as nested functions so they don't clobber the
# pydoc-generated docs
def _test_():
name = ''
print '#'*50+'\nRunning test for ' + name
# ...
print 'Finished test for '+ name +'\n'+'#'*50
def _test_OutputTrap():
trap = OutputTrap(name = 'Test Trap', sum_sep = '.'*50+'\n',
out_head = 'SOut. ', err_head = 'SErr. ')
name = 'OutputTrap class'
print '#'*50+'\nRunning test for ' + name
print 'Trapping out'
trap.trap_out()
print >>sys.stdout, '>>stdout. stdout is trapped.'
print >>sys.stderr, '>>stderr. stdout is trapped.'
trap.release_out()
print trap.summary_out()
print 'Trapping err'
trap.trap_err()
print >>sys.stdout, '>>stdout. stderr is trapped.'
print >>sys.stderr, '>>stderr. stderr is trapped.'
trap.release_err()
print trap.summary_err()
print 'Trapping all (no flushing)'
trap.trap_all()
print >>sys.stdout, '>>stdout. stdout/err is trapped.'
print >>sys.stderr, '>>stderr. stdout/err is trapped.'
trap.release_all()
print trap.summary_all()
print 'Trapping all (flushing first)'
trap.flush()
trap.trap_all()
print >>sys.stdout, '>>stdout. stdout/err is trapped.'
print >>sys.stderr, '>>stderr. stdout/err is trapped.'
trap.release_all()
print trap.summary_all()
print 'Finished test for '+ name +'\n'+'#'*50
# call the actual tests here:
_test_OutputTrap()
if __name__=="__main__":
# _test_all() # XXX BROKEN.
pass
#************************ end of file <OutputTrap.py> ************************
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