How to pass python function to another function with flag

Question

I have created verbose_on (it shows output if used) and verbose_off fuction. In verbose_on(fn), fn is another function.

helper.py

import os
import sys
import io
def verbose_on(fn):
    sys.stdout = io.StringIO()
    fn()
    output = sys.stdout.getvalue()
    sys.stdout = sys.__stdout__
    print(output)


def verbose_off(fn):
    sys.stdout = io.StringIO()
    fn()
    sys.stdout = sys.__stdout__
    print('Task Completed.')

/dev.py

In sample function there are some commands, whose output need to be showed in test function if verbose is on.

def sample(flag2):
    print('tests are running')
    # another commands running

/main.py

It has test function which has two flags, one to activate verbose and another flag which is needed to pass with sample. Check helper.verbose_off(sample) in test function, it is passing sample which will be converted to function in verbose_on method(fn(), i.e. sample())

from dev import sample
from helper import verbose_on, verbose_off
def test(verbose, flag2):
    if verbose:
        print('Verbose mode = On.')
        helper.verbose_on(sample)
    else:
        print('Verbose mode = Off')
        helper.verbose_off(sample)

But it is needed that flag2 shoud be pass with sample inside test function, something like this : helper.verbose_on(sample(flag2)). Any suggestions will be appreciated. Thank you in advance.

Don't forget the function itself, i.e. def verbose_on(fn, *args, **kwargs), that calls fn(*args, **kwargs), and you call verbose_on(sample, flag2) — tobias_k
– tobias_k, Commented Jul 27, 2022 at 16:56

vdorot · Accepted Answer · 2022-07-27 16:15:36Z

2

Use lambda functions:

def test(verbose, flag2):
    if verbose:
        print('Verbose mode = On.')
        helper.verbose_on(lambda: sample(flag2))

or functools.partial:

def test(verbose, flag2):
    if verbose:
        print('Verbose mode = On.')
        helper.verbose_on(functools.partial(sample, flag2))

answered Jul 27, 2022 at 16:15

vdorot

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2 Comments

Sammlona Over a year ago

if we use functools.partial then do we need to do changes in verbose_on method?

vdorot Over a year ago

No, functools.partial will return a callable object, which will be called by the fn() statement in verbose_on/off. Even after the change, only one argument is passed to verbose_on/off.

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