Using given parameter as a default value for another paramater in Python

Question

I want to have the following heading where the default value of a parameter depends on another parameter:

def function2(x,l=0,r=len(x)-1)

This obviously returns an error. Is there any way to go around this?

Thank you

But that would override those cases where `r` is not equal to `len(x)-1`, right? — zest16, Jan 16 '20 at 23:08
@zest16 You can play around with the parameter inside the function. `def function2(x, l, r): r = len(x)-1 ... — dper, Jan 16 '20 at 23:09
Does this help? https://stackoverflow.com/questions/21804615/how-can-i-make-the-default-value-of-an-argument-depend-on-another-argument-in-p — Anis R., Jan 16 '20 at 23:10

score 3 · Accepted Answer · answered Jan 16 '20 at 23:09

3

This workaround maybe can help:

def function2(x, l=0, r=None):
    if r is None:
        r = len(x) - 1
    ...

This will set r to len(x) - 1 only when r is not set, i.e:

function2(x='hi', l=0)  # r will take value len(x) - 1
function2(x='hi', l=0, r=5)  # r will take value 5

answered Jan 16 '20 at 23:09

Gocht

score 0 · Answer 2 · answered Jan 16 '20 at 23:10

0

I am not sure if this solution will completely help you.

If a variable depends on another input variable it might be interesting to do something like:

def function2(x,l=0):
     r = len(x) - 1
     ...

answered Jan 16 '20 at 23:10

jalazbe

OP still wants `r` to be a parameter of the function, but with a default value of `len(x) - 1`. – Anis R. Jan 16 '20 at 23:11

2 Answers2