[Python-Dev] A grammatical oddity: trailing commas in argument lists -- continuation (original) (raw)

Jan Kaliszewski zuo at chopin.edu.pl
Mon Dec 13 15🔞34 CET 2010

Nick Coghlan dixit (2010-12-13, 23:25):

Function arguments are not lists. Even when separated onto multiple lines, the closing "):" should remain on the final line with other content.

Not necessarily, IMHO.

  1. What about my example with '-> xxx' return-value annotation? (especially when that annotation is a long expression)

  2. There are two argument-list-formatting idioms I apply -- depending on which is more suitable in a particular case:

a) when argument specs/expressions are not very long and rather if their number is not very big:

def function(argument_spec1, argument_spec2, argument_spec3,
             argument_spec4, argument_spec5, argument_spec6):

function_call(expression1, expression2, expression3,
              expression4, expression5, expression6)

b) for long argument lists and/or argument specs/expressions (e.g. when default values or argument annotations are defined as long expressions):

def function(
    long_argument_spec1,
    long_argument_spec2,
    long_argument_spec3,
    long_argument_spec4,
    long_argument_spec5,
    long_argument_spec6,
):

function_call(
    long_expression1,
    long_expression2,
    long_expression3,
    long_expression4,
    long_expression5,
    long_expression6,
)

Note that option 'b' is more convenient for refactorization, diffs etc.

Regards, *j

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