Python alternative to Javascript function.bind()? [duplicate]

Question

In Javascript, one might write

var ids = ['item0', 'item1', 'item2', 'item3']; // variable length
function click_callback(number, event)
{
    console.log('this is: ', number);
}
for (var k = 0; k < ids.length; k += 1)
{
    document.getElementById(ids[k]).onclick = click_callback.bind(null, k);
}

So I can pass to the callback function the value of k at the time it is registered even though it has changed by the time the function is called.

Does Python have a way to do something equivalent?

The specific situation is this (but I prefer a general answer):

I have a variable number of matplotlib plots (one for each coordinate). Each has a SpanSelector, which was for some reason designed to only pass the two limit points to the callback function. However, they all have the same callback function. So I have:

def span_selected(min, max):

but I need

def span_selected(which_coordinate, min, max):

At the time of registering the callback, I of course know the coordinate, but I need to know it when the function is called. In Javascript, I would do something like

callback = span_selected.bind(null, coordinate)

What would I do in Python?

I found the answer here on SO shortly after posting this (writing it down helps construct better search queries apparently). Should I delete the question as a duplicate, or answer it so other people who use javascript related search words might find the solution more easily? — Mark
– Mark, Commented Oct 7, 2013 at 5:27
I don't quite get what you mean by "one for each coordinate". If you have multiple plots, I think you should have a separate SpanSelector for each plot. — BrenBarn
– BrenBarn, Commented Oct 7, 2013 at 5:27
What is the duplicate question? Often better to mark it as duplicate so it's still findable as a signpost to the answer. — BrenBarn
– BrenBarn, Commented Oct 7, 2013 at 5:28
Okay I'll do that, and I'll edit to clarify the part about SpanSelectors — Mark
– Mark, Commented Oct 7, 2013 at 5:29

Community · Accepted Answer · 2017-05-23 12:21:37Z

7

Turned out it was already answered here: How to bind arguments to given values in Python functions?

The solution is:

from functools import partial
def f(a,b,c):
    print a,b,c
bound_f = partial(f,1)
bound_f(2,3)

Full credits to MattH.

EDIT: so in the example, instead of

callback = span_selected.bind(null, coordinate)

use

callback = partial(span_selected, coordinate)

edited May 23, 2017 at 12:21

CommunityBot

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answered Oct 7, 2013 at 5:31

Mark

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