Pipe console outputs from a specific function into a file - python

Question

I have a function that I cannot edit and it prints results onto the console. Is it possible to calls that function but pipes the console output into a file without changing the internal code of the function?

For example, I have:

def somefunc(x):
  print "Hello World", x**x

def pipeout(func, outfilename)
  with open('outfilename', 'w') as fout:
    # somehow pipes out the output...

I couldn't use logger because I couldn't edit the somefunc().

I have tried @Aशwini चhaudhary 's solution but i couldn't the files were empty other than the first outputfile and also it overwrites that file again and again.:

def redirect_output(file_name):
  def decorator(func):
    def wrapper(*args):
      with open(file_name, 'w') as f:
        original_stdout = sys.stdout
        sys.stdout = f
        func(*args)
      sys.stdout = original_stdout
    return wrapper
  return decorator

def somefunc(x):
  print x*x

xs = [1,2,3,4]

for i in xs:
  outputfilename = 'results/'+str(i)
  somefunc = redirect_output(outputfilename)(somefunc)
  somefunc(i)

Answer 1

You can use a decorator to redirect the sys.stdout to a file object when the function gets called and later restores it back to original STDOUT.

import sys

def redirect_output(file_name):

    def decorator(func):
        def wrapper(*args):
            with open(file_name, 'w') as f:
                original_stdout = sys.stdout
                sys.stdout = f
                func(*args)
            sys.stdout = original_stdout
        return wrapper
    return decorator

@redirect_output('file.txt')
def somefunc(x):
  print "Hello World", x**x


somefunc(2)

print 'Hello to console.'

Output:

>>> %run so.py
Hello to console.
>>> !cat file.txt
Hello World 4

Update:

Working version of your latest code:

for i in xs:
  outputfilename = 'results/'+str(i)
  new_func = redirect_output(outputfilename)(somefunc)
  #or call it directly
  #redirect_output(outputfilename)(somefunc)(i)
  new_func(i)