Python: avoiding Pylint warnings about too many arguments

Question

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)

Do you want a better way to pass the arguments or just a way to stop Pylint from giving you a hard time? If the latter, you can stop the nagging by putting Pylint-controlling comments in your code along the lines of:

#pylint: disable=R0913

or, better:

#pylint: disable=too-many-arguments

remembering to turn them back on as soon as practicable.

In my opinion, there's nothing inherently wrong with passing a lot of arguments and solutions advocating wrapping them all up in some container argument don't really solve any problems, other than stopping Pylint from nagging you :-).

If you need to pass twenty arguments, then pass them. It may be that this is required because your function is doing too much and refactoring could assist there, and that's something you should look at. But it's not a decision we can really make unless we see what the 'real' code is.

You can easily change the maximum allowed number of arguments in Pylint. Just open your pylintrc file (generate it if you don't already have one) and change:

max-args = 5

to:

max-args = 6 # Or any value that suits you

From Pylint's manual

Specifying all the options suitable for your setup and coding standards can be tedious, so it is possible to use a rc file to specify the default values. Pylint looks for /etc/pylintrc and ~/.pylintrc. The --generate-rcfile option will generate a commented configuration file according to the current configuration on standard output and exit. You can put other options before this one to use them in the configuration, or start with the default values and hand tune the configuration.

You could try using Python's variable arguments feature:

def myfunction(*args):
    for x in args:
        # Do stuff with specific argument here

Perhaps you could turn some of the arguments into member variables. If you need that much state a class sounds like a good idea to me.

I do not like referring to the number. The symbolic name is much more expressive and avoid having to add a comment that could become obsolete over time.

So I'd rather do:

#pylint: disable-msg=too-many-arguments

And I would also recommend to not leave it dangling there: it will stay active until the file ends or it is disabled, whichever comes first.

So better do:

#pylint: disable-msg=too-many-arguments
code_which_would_trigger_the_msg
#pylint: enable-msg=too-many-arguments

I would also recommend enabling/disabling one single warning/error per line.