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

User · Answer

Python has some nice functional programming tools that are likely to fit your needs well. Check out lambda functions and map. Also, you're using dicts when it seems like you'd be much better served with lists. For the simple example you provided, try this idiom. Note that map would be better and faster but may not fit your needs:

def mysum(d):
   s = 0  
   for x in d:
        s += x
   return s

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

You mentioned having a lot of local variables, but frankly if you're dealing with lists (or tuples), you should use lists and factor out all those local variables in the long run.

User · Answer

I came across the same nagging error  which I realized has something to do with a cool feature PyCharm automatically detects   just add the  staticmethod decorator  and it will automatically remove that error where the method is used

User · Answer

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

User · Answer

You could try using Python s variable arguments feature   def myfunction  args       for x in args            Do stuff with specific argument here

User · Answer

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

User · Answer

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  I seem to recall that you could 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 a re-factoring 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

User · Answer

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

User · Answer

I do not like referring to the number  the sybolic 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 doing    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

User · Answer

Simplify or break apart the function so that it doesn t require nine arguments  or ignore pylint  but dodges like the ones you re proposing defeat the purpose of a lint tool    EDIT  if it s a temporary measure  disable the warning for the particular function in question using a comment as described here  http   lists logilab org pipermail python-projects 2006-April 000664 html  Later  you can grep for all of the disabled warnings

[python] Python: avoiding pylint warnings about too many arguments

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