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pythoncallbackdefault-parameters
Pedro Contipelli
Pedro Contipelli

Reputation: 387

How to write a default parameter callback function that does nothing? [Python]

I sometimes want to pass in a callback function as a parameter to my_function. However, I want the default behavior to simply do nothing.

I find myself wanting to write the following invalid lines of code:

def my_function(args, callback_function=pass):
    # do something
    callback_function()

But that doesn't work, so the best valid solution I have come up with is:

def do_nothing():
    pass

def my_function(args, callback_function=do_nothing):
    # do something
    callback_function()

Is there a cleaner way to do this, more like the first example above?

Upvotes: 1

Views: 393

Answers (2)

Daweo
Daweo

Reputation: 36340

You might elect to accept None and only call callback_function when it is not None, that is

def my_function(args, callback_function=None):
  # do something
  if callback_function is not None:
      callback_function()

Upvotes: 2

CDubyuh
CDubyuh

Reputation: 146

Calling 'None' should do what you're asking. 'pass' is a keyword and is not callable like that. None is a default value and can be applied using lambda.

 def my_function(args, callback_function=lambda: None):
        # do something
        callback_function()

Upvotes: 2

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