Here is an easy way to temporarily turn off STDOUT or STDERR in your Python program.
First you create a class to replace STDOUT. This is just minimal class with a 'write()' method.
class NullDevice():
def write(self, s):
pass
Notice its 'write()' method does nothing. Therefore, when you write to the NullDevice, output goes nowhere and is dropped. All you need to do is assign sys.stdout to this class.
Here is an example of turning STDOUT off and back on:
#!/usr/bin/env python
import sys
class NullDevice():
def write(self, s):
pass
print "1 - this will print to STDOUT"
original_stdout = sys.stdout # keep a reference to STDOUT
sys.stdout = NullDevice() # redirect the real STDOUT
print "2 - this won't print"
sys.stdout = original_stdout # turn STDOUT back on
print "3 - this will print to SDTDOUT"
You can also do the same thing with sys.stderr to turn off STDERR.
9 comments:
Or just sys.stdout = open('/dev/null') if you're using a unix based system..
right.. but like you said, that's not a portable solution.
sys.stdout = open(os.devnull, 'w') should be pretty portable.
thanks eMBe!
You can also not backup the original sys.stdout and restore it using sys.stdout == sys.__stdout__
in short thanks for the information.
hmm... Portable solution:
sys.stderr = None
No @Kalmi, None does not allow other statements to .write() to it, causing an exception to be raised.
No, @Roms: some previous code, e.g. unit-test tool, may use some not-default stderr, so backup with restoring in any case is good idea:
import sys, os
old_stderr = sys.stderr
sys.stderr = open(os.devnull, 'w')
try:
some_code_that_writes_to_stderr()
finally:
sys.stderr.close()
sys.stderr = old_stderr
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