Hook on stdout and stderr so that we can handle printing of text,error differently e.g in GUI base application divert text to a log window.
Python, 95 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 | import sys
#this class gets all output directed to stdout(e.g by print statements)
#and stderr and redirects it to a user defined function
class PrintHook:
#out = 1 means stdout will be hooked
#out = 0 means stderr will be hooked
def __init__(self,out=1):
self.func = None##self.func is userdefined function
self.origOut = None
self.out = out
#user defined hook must return three variables
#proceed,lineNoMode,newText
def TestHook(self,text):
f = open('hook_log.txt','a')
f.write(text)
f.close()
return 0,0,text
def Start(self,func=None):
if self.out:
sys.stdout = self
self.origOut = sys.__stdout__
else:
sys.stderr= self
self.origOut = sys.__stderr__
if func:
self.func = func
else:
self.func = self.TestHook
#Stop will stop routing of print statements thru this class
def Stop(self):
self.origOut.flush()
if self.out:
sys.stdout = sys.__stdout__
else:
sys.stderr = sys.__stderr__
self.func = None
#override write of stdout
def write(self,text):
proceed = 1
lineNo = 0
addText = ''
if self.func != None:
proceed,lineNo,newText = self.func(text)
if proceed:
if text.split() == []:
self.origOut.write(text)
else:
#if goint to stdout then only add line no file etc
#for stderr it is already there
if self.out:
if lineNo:
try:
raise "Dummy"
except:
newText = 'line('+str(sys.exc_info()[2].tb_frame.f_back.f_lineno)+'):'+newText
codeObject = sys.exc_info()[2].tb_frame.f_back.f_code
fileName = codeObject.co_filename
funcName = codeObject.co_name
self.origOut.write('file '+fileName+','+'func '+funcName+':')
self.origOut.write(newText)
#pass all other methods to __stdout__ so that we don't have to override them
def __getattr__(self, name):
return self.origOut.__getattr__(name)
if __name__ == '__main__':
def MyHookOut(text):
return 1,1,'Out Hooked:'+text
def MyHookErr(text):
f = open('hook_log.txt','a')
f.write(text)
f.close()
return 1,1,'Err Hooked:'+text
print 'Hook Start'
phOut = PrintHook()
phOut.Start(MyHookOut)
phErr = PrintHook(0)
phErr.Start(MyHookErr)
print 'Is this working?'
print 'It seems so!'
phOut.Stop()
print 'STDOUT Hook end'
compile(',','<string>','exec')
phErr.Stop()
print 'Hook end'
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User use can use the class PrintHook to divert all output to stdout and stderr so that it passes thru a user given function. Where we can manipulate the text.
User can also separate messages for stderr from stdout to a different file, function etc.
Tags: debugging
Kindly let me know if this can be used to include a watermark only on specific files. i.e if a file is named with the word Text, then a watermark written sample is added when the file is printed. Other files not named so are excluded from the watermark.Urgently advice.