Python: avoiding pylint warnings about too many arguments

Question

I want to refactor a big Python function into smaller ones. For example, consider this following code snippet:

x = x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9

Of course, this is a trivial example. In practice, the code is more complex. My point is that it contains many local-scope variables that would have to be passed to the extracted function, which could look like:

def mysum(x1, x2, x3, x4, x5, x6, x7, x8, x9):
    x = x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9
    return x

The problem is that pylint would trigger a warning about too many arguments. I could avoid the warning by doing something like:

def mysum(d):
    x1 = d['x1']
    x2 = d['x2']
    ...
    x9 = d['x9']
    x = x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 + x9
    return x

def mybigfunction():
    ...
    d = {}
    d['x1'] = x1
    ...
    d['x9'] = x9
    x = mysum(d)

but this approach loos ugly to me, it requires writing a lot of code that is even redundant.

Is there a better way to do it?

Answer 1

First, one of Perlis's epigrams:

"If you have a procedure with 10 parameters, you probably missed some."

Some of the 10 arguments are presumably related. Group them into an object, and pass that instead.

Making an example up, because there's not enough information in the question to answer directly:

class PersonInfo(object):
  def __init__(self, name, age, iq):
    self.name = name
    self.age = age
    self.iq = iq

Then your 10 argument function:

def f(x1, x2, name, x3, iq, x4, age, x5, x6, x7):
  ...

becomes:

def f(personinfo, x1, x2, x3, x4, x5, x6, x7):
  ...

and the caller changes to:

personinfo = PersonInfo(name, age, iq)
result = f(personinfo, x1, x2, x3, x4, x5, x6, x7)