Pythonic way to pass optional parameter by variable name

Question

I'm sorry if the question is a bit unclear, I'm not sure how to phrase it.

I'm working with a package that has a function with a number of optional parameters. Say there are three parameters: x, y, z. I will always pass the same value, just to a different parameter. So I could do this:

if setting is x:
    package.someFunction(x=1)
elif setting is y:
    package.someFunction(y=1)
elif setting is z:
    package.someFunction(z=1)

Is there a more pythonic way to do it? Can I assign the parameter name to some variable pass it that way?

Morgan Thrapp · Accepted Answer · 2016-08-04 20:31:41Z

5

I would build a dictionary with setting as the key and the static value as the value. This way, you don't have to do that awkward switching.

For example:

setting = 'x'
kwargs = {setting: 1}
package.someFunction(**kwargs)

Just change the setting = 'x' line to be however you're getting that setting. It just needs to equal the name of the argument in package.someFunction that you want to apply the value to.

edited Aug 4, 2016 at 20:31

answered Aug 4, 2016 at 20:29

Morgan Thrapp

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4 Comments

Niel Over a year ago

So setting would just be 'x' or 'z'? That's great, thanks!

Morgan Thrapp Over a year ago

@Niel Exactly. You'd have setting be a string with the name of the argument.

chepner Over a year ago

You don't even need the variable for the argument; you can pass a dict literal: package.someFunction(**{setting: 1}).

Morgan Thrapp Over a year ago

@chepner Yeah, normally that's how I'd do it. I'm just breaking it down to make each step clearer.

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