CODEWITHSUNDEEP
pythonpython-2.7
dopatraman
dopatraman

Reputation: 13908

Reference function's scope while inside another function

I want to pass a function into another function, but use the scope of the second function inside the first. I have a javascript background, so I'm used to doing things like:

function write(str, path) {
    // do stuff
}

function doThis(fn) {
    fn()
}

function doThisString(str, path) {
    doThis(function() {
      write(str, path)
    });
}

How can i do this in python?

Upvotes: 0

Views: 60

Answers (3)

markcial
markcial

Reputation: 9323

Here is how it would look syntactically in python:

def write(text, path):
    // do stuff

def doThis(fn):
    fn()

def doThisString(text, path):
   doThis(lambda: write(text, path) )

Upvotes: 0

user395760
user395760

Reputation:

Yes, Python supports closures. But except for the very limited (only a single expression) lambda form, functions must be defined in a separate statement before being used - they can't be created in an expression.

If you want to avoid nested function definitions for the sake of avoiding nesting, you can use functools.partial. Your specific example would be greatly simplified by it anyway:

from functools import partial

def doThisString(str, path):
    doThis(partial(write, str, path))

It doesn't always work out that well, so sometimes there are better alternatives.

Upvotes: 2

Hyperboreus
Hyperboreus

Reputation: 32429

The python equivalent would be.

def write (mystr, path): pass

def doThis (f): f ()

def doThisString (mystr, path):
    doThis (lambda: write (mystr, path) )

Or alternatively:

def doThisString (mystr, path):
    def function (): write (mystr, path)
    doThis (function)

Upvotes: 2

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