'How to block calls to print?
Is there a way to stop a function from calling print?
I am using the pygame.joystick module for a game I am working on.
I created a pygame.joystick.Joystick object and in the actual loop of the game call its member function get_button to check for user input. The function does everything I need it to do, but the problem is that it also calls print, which slows down the game considerably.
Can I block this call to print?
Solution 1:[1]
Python lets you overwrite standard output (stdout) with any file object. This should work cross platform and write to the null device.
import sys, os
# Disable
def blockPrint():
sys.stdout = open(os.devnull, 'w')
# Restore
def enablePrint():
sys.stdout = sys.__stdout__
print 'This will print'
blockPrint()
print "This won't"
enablePrint()
print "This will too"
If you don't want that one function to print, call blockPrint() before it, and enablePrint() when you want it to continue. If you want to disable all printing, start blocking at the top of the file.
Solution 2:[2]
Use with
Based on @FakeRainBrigand solution I'm suggesting a safer solution:
import os, sys
class HiddenPrints:
def __enter__(self):
self._original_stdout = sys.stdout
sys.stdout = open(os.devnull, 'w')
def __exit__(self, exc_type, exc_val, exc_tb):
sys.stdout.close()
sys.stdout = self._original_stdout
Then you can use it like this:
with HiddenPrints():
print("This will not be printed")
print("This will be printed as before")
This is much safer because you can not forget to re-enable stdout, which is especially critical when handling exceptions.
Without with — Bad practice
The following example uses enable/disable prints functions that were suggested in previous answer.
Imagine that there is a code that may raise an exception. We had to use finally statement in order to enable prints in any case.
try:
disable_prints()
something_throwing()
enable_prints() # This will not help in case of exception
except ValueError as err:
handle_error(err)
finally:
enable_prints() # That's where it needs to go.
If you forgot the finally clause, none of your print calls would print anything anymore.
It is safer to use the with statement, which makes sure that prints will be reenabled.
Note: It is not safe to use sys.stdout = None, because someone could call methods like sys.stdout.write()
Solution 3:[3]
As @Alexander Chzhen suggested, using a context manager would be safer than calling a pair of state-changing functions.
However, you don't need to reimplement the context manager - it's already in the standard library. You can redirect stdout (the file object that print uses) with contextlib.redirect_stdout, and also stderr with contextlib.redirect_stderr.
import os
import contextlib
with open(os.devnull, "w") as f, contextlib.redirect_stdout(f):
print("This won't be printed.")
Solution 4:[4]
If you want to block print calls made by a particular function, there is a neater solution using decorators. Define the following decorator:
# decorater used to block function printing to the console
def blockPrinting(func):
def func_wrapper(*args, **kwargs):
# block all printing to the console
sys.stdout = open(os.devnull, 'w')
# call the method in question
value = func(*args, **kwargs)
# enable all printing to the console
sys.stdout = sys.__stdout__
# pass the return value of the method back
return value
return func_wrapper
Then just place @blockPrinting before any function. For example:
# This will print
def helloWorld():
print("Hello World!")
helloWorld()
# This will not print
@blockPrinting
def helloWorld2():
print("Hello World!")
helloWorld2()
Solution 5:[5]
If you are using Jupyter Notebook or Colab use this:
from IPython.utils import io
with io.capture_output() as captured:
print("I will not be printed.")
Solution 6:[6]
I have had the same problem, and I did not come to another solution but to redirect the output of the program (I don't know exactly whether the spamming happens on stdout or stderr) to /dev/null nirvana.
Indeed, it's open source, but I wasn't passionate enough to dive into the pygame sources - and the build process - to somehow stop the debug spam.
EDIT :
The pygame.joystick module has calls to printf in all functions that return the actual values to Python:
printf("SDL_JoystickGetButton value:%d:\n", value);
Unfortunately you would need to comment these out and recompile the whole thing. Maybe the provided setup.py would make this easier than I thought. You could try this...
Solution 7:[7]
A completely different approach would be redirecting at the command line. If you're on Windows, this means a batch script. On Linux, bash.
/full/path/to/my/game/game.py > /dev/null
C:\Full\Path\To\My\Game.exe > nul
Unless you're dealing with multiple processes, this should work. For Windows users this could be the shortcuts you're creating (start menu / desktop).
Solution 8:[8]
You can do a simple redirection, this seems a lot safer than messing with stdout, and doesn't pull in any additional libraries.
enable_print = print
disable_print = lambda *x, **y: None
print = disable_print
function_that_has_print_in_it(1) # nothing is printed
print = enable_print
function_that_has_print_in_it(2) # printing works again!
Note: this only works to disable the print() function, and would not disable all output if you're making calls to something else that is producing output. For instance if you were calling a C library that was producing it's own output to stdout, or if you were using intput().
Solution 9:[9]
No, there is not, especially that majority of PyGame is written in C.
But if this function calls print, then it's PyGame bug, and you should just report it.
Solution 10:[10]
The module I used printed to stderr. So the solution in that case would be:
sys.stdout = open(os.devnull, 'w')
Solution 11:[11]
Based on @Alexander Chzhen solution, I present here the way to apply it on a function with an option to suppress printing or not.
import os, sys
class SuppressPrints:
#different from Alexander`s answer
def __init__(self, suppress=True):
self.suppress = suppress
def __enter__(self):
if self.suppress:
self._original_stdout = sys.stdout
sys.stdout = open(os.devnull, 'w')
def __exit__(self, exc_type, exc_val, exc_tb):
if self.suppress:
sys.stdout.close()
sys.stdout = self._original_stdout
#implementation
def foo(suppress=True):
with SuppressPrints(suppress):
print("It will be printed, or not")
foo(True) #it will not be printed
foo(False) #it will be printed
I hope I can add my solution below answer of Alexander as a comment, but I don`t have enough (50) reputations to do so.
Solution 12:[12]
"stop a function from calling print"
# import builtins
# import __builtin__ # python2, not test
printenabled = False
def decorator(func):
def new_func(*args,**kwargs):
if printenabled:
func("print:",*args,**kwargs)
return new_func
print = decorator(print) # current file
# builtins.print = decorator(builtins.print) # all files
# __builtin__.print = decorator(__builtin__.print) # python2
import sys
import xxxxx
def main():
global printenabled
printenabled = True
print("1 True");
printenabled = False
print("2 False");
printenabled = True
print("3 True");
printenabled = False
print("4 False");
if __name__ == '__main__':
sys.exit(main())
#output
print: 1 True
print: 3 True
Solution 13:[13]
Change value of file object of print() function. By default it's sys.stdout, instead we can write to null device by open(os.devnull, 'w')
import os, sys
mode = 'debug' #'prod'
if mode == 'debug':
fileobj = sys.stdout
else:
fileobj = open(os.devnull,'w')
print('Hello Stackoverflow', file = fileobj)
Sources
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Source: Stack Overflow