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I have a set of python scripts (script<X>.py). All scripts have a run() function, which should be executed in a new Process. The execution is triggered by a web server (server.py), which imports all scripts. I have access to the server code only.

Is there a way to redirect the script's stdout to a separate file?

In a simplified form the setup looks like this:

=== script1.py ===
def run(**kwargs):
   <do stuff>
   print(<stuff>)

=== server.py ===
import multiprocessing
import script1

p = multiprocessing.Process(target=script1.run) # <--- This output should be written to file, e.g. script1.txt
p.start()

Update: (ugly) workaround

As suggested in Log output of multiprocessing.Process it helps to replace sys.stdout by the desired file handle in the target function. As my target function lies in a different module , which I am not allowed to change, I manipulated the code text during the import step.

=== script1.py ===
def run(**kwargs):
   <do stuff>
   print(<stuff>)

=== server.py ===
import multiprocessing
import importlib

def replace_stdout(code):
    """ Function to add sys.stdout = open(<file>) in run()"""
    replaced_code = []
    code_lines = code.split('\n')
    for i,line in enumerate(code_lines):
        replaced_code.append(line)
        if line.startswith("def run(") : 
            # Check indentation if tab or spaces
            indent = "\t" if code_lines[i+1][0] == '\t' else " "*( len(line.strip())-len(line))
            # Add line to code
            replaced_code.append(f'{indent}import sys') 
            replaced_code.append(f'{indent}sys.stdout=open("script1.txt","a")')
    return "\n".join(replaced_code)

# Read script code from file, manipulate target function code and create module object
code = replace_stdout( open("script1.py","r").read() )
spec = importlib.util.spec_from_loader('script1', loader=None)
module_script1 = importlib.util.module_from_spec(spec)
exec(code, module_script1 .__dict__)

p = multiprocessing.Process(target=module_script1 .run) # <--- This output should be written to file, e.g. script1.txt
p.start()
Tomas Pazur
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  • Instead of running script1.py directly, run a shell that starts script1.py and does redirection. E.g. "sh -c 'python script1.p1 >script1-out.txt" on Linux. – Dov Grobgeld Dec 24 '20 at 14:23
  • Does this answer your question? [Log output of multiprocessing.Process](https://stackoverflow.com/questions/1501651/log-output-of-multiprocessing-process) – Arkadiusz Drabczyk Dec 24 '20 at 14:26
  • @ArkadiuszDrabczyk This works, but I am not allowed to change the imported script's code to add sys.stdout = open("script1.txt","a"). Nevertheless , I made a (ugly) workaround , which manipulates the code text during import and adds the line after the def run(): . – Tomas Pazur Dec 25 '20 at 10:55

0 Answers0