suggestions on passing a json as a function input












0















I am planning to write a routine to achieve below functionality: According to the "method", and "before" and "after", compute the expense. Not sure if passing a json as an input of the function is a good practice? Does it mean the function is trying to achieve too much? When I assign a default value to "target", Pycharm gives warning "mutable object as default argument".



def assign_expense(target={'fly':{'before':'US', 'after':'JP'}, 'walk':{'before':'blockA', 'after':'blockB'})

  method, before, after = abstract_param_from_json(target)

  if method='fly':

      if before=='US', after=='JP':

          func_fly_US_JP



      elif before=='MXN', after=='CAD':

          func_fly_MX_CAD

  if method='walk':

      if before=='blockA', after=='blockB':

               func_A_to_B



      if before=='blockC', after=='blockZ':

               func_C_to_Z





python







share|improve this question


















  • 1





    You should be very careful about mutable default arguments. They don't necessarily behave the way you think they should (hence the warning from Pycharm).

    – Jonah Bishop
    Nov 27 '18 at 1:47


















0















I am planning to write a routine to achieve below functionality: According to the "method", and "before" and "after", compute the expense. Not sure if passing a json as an input of the function is a good practice? Does it mean the function is trying to achieve too much? When I assign a default value to "target", Pycharm gives warning "mutable object as default argument".



def assign_expense(target={'fly':{'before':'US', 'after':'JP'}, 'walk':{'before':'blockA', 'after':'blockB'})

  method, before, after = abstract_param_from_json(target)

  if method='fly':

      if before=='US', after=='JP':

          func_fly_US_JP



      elif before=='MXN', after=='CAD':

          func_fly_MX_CAD

  if method='walk':

      if before=='blockA', after=='blockB':

               func_A_to_B



      if before=='blockC', after=='blockZ':

               func_C_to_Z





python







share|improve this question


















  • 1





    You should be very careful about mutable default arguments. They don't necessarily behave the way you think they should (hence the warning from Pycharm).

    – Jonah Bishop
    Nov 27 '18 at 1:47
















0












0








0








I am planning to write a routine to achieve below functionality: According to the "method", and "before" and "after", compute the expense. Not sure if passing a json as an input of the function is a good practice? Does it mean the function is trying to achieve too much? When I assign a default value to "target", Pycharm gives warning "mutable object as default argument".



def assign_expense(target={'fly':{'before':'US', 'after':'JP'}, 'walk':{'before':'blockA', 'after':'blockB'})

  method, before, after = abstract_param_from_json(target)

  if method='fly':

      if before=='US', after=='JP':

          func_fly_US_JP



      elif before=='MXN', after=='CAD':

          func_fly_MX_CAD

  if method='walk':

      if before=='blockA', after=='blockB':

               func_A_to_B



      if before=='blockC', after=='blockZ':

               func_C_to_Z





python







share|improve this question














I am planning to write a routine to achieve below functionality: According to the "method", and "before" and "after", compute the expense. Not sure if passing a json as an input of the function is a good practice? Does it mean the function is trying to achieve too much? When I assign a default value to "target", Pycharm gives warning "mutable object as default argument".



def assign_expense(target={'fly':{'before':'US', 'after':'JP'}, 'walk':{'before':'blockA', 'after':'blockB'})

  method, before, after = abstract_param_from_json(target)

  if method='fly':

      if before=='US', after=='JP':

          func_fly_US_JP



      elif before=='MXN', after=='CAD':

          func_fly_MX_CAD

  if method='walk':

      if before=='blockA', after=='blockB':

               func_A_to_B



      if before=='blockC', after=='blockZ':

               func_C_to_Z





python




python






share|improve this question













share|improve this question











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asked Nov 27 '18 at 1:40









LisaLisa

1,00511537




1,00511537








  • 1





    You should be very careful about mutable default arguments. They don't necessarily behave the way you think they should (hence the warning from Pycharm).

    – Jonah Bishop
    Nov 27 '18 at 1:47
















  • 1





    You should be very careful about mutable default arguments. They don't necessarily behave the way you think they should (hence the warning from Pycharm).

    – Jonah Bishop
    Nov 27 '18 at 1:47










1




1





You should be very careful about mutable default arguments. They don't necessarily behave the way you think they should (hence the warning from Pycharm).

– Jonah Bishop
Nov 27 '18 at 1:47







You should be very careful about mutable default arguments. They don't necessarily behave the way you think they should (hence the warning from Pycharm).

– Jonah Bishop
Nov 27 '18 at 1:47














1 Answer
1






active

oldest

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2














Regarding your warning mutable object as default argument



Please refer the following



https://docs.quantifiedcode.com/python-anti-patterns/correctness/mutable_default_value_as_argument.html



"Least Astonishment" and the Mutable Default Argument



Mutable objects as default arguments behave like a static variable



And regarding passing JSON as function input, I don't think it is a bad practice by itself unless the function is doing many things on the JSON.



Ex: If you need to delete/process a particular set of keys in the JSON, you need to pass JSON to the function that does the job.






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    active

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    active

    oldest

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    active

    oldest

    votes






    active

    oldest

    votes









    2














    Regarding your warning mutable object as default argument



    Please refer the following



    https://docs.quantifiedcode.com/python-anti-patterns/correctness/mutable_default_value_as_argument.html



    "Least Astonishment" and the Mutable Default Argument



    Mutable objects as default arguments behave like a static variable



    And regarding passing JSON as function input, I don't think it is a bad practice by itself unless the function is doing many things on the JSON.



    Ex: If you need to delete/process a particular set of keys in the JSON, you need to pass JSON to the function that does the job.






    share|improve this answer




























      2














      Regarding your warning mutable object as default argument



      Please refer the following



      https://docs.quantifiedcode.com/python-anti-patterns/correctness/mutable_default_value_as_argument.html



      "Least Astonishment" and the Mutable Default Argument



      Mutable objects as default arguments behave like a static variable



      And regarding passing JSON as function input, I don't think it is a bad practice by itself unless the function is doing many things on the JSON.



      Ex: If you need to delete/process a particular set of keys in the JSON, you need to pass JSON to the function that does the job.






      share|improve this answer


























        2












        2








        2







        Regarding your warning mutable object as default argument



        Please refer the following



        https://docs.quantifiedcode.com/python-anti-patterns/correctness/mutable_default_value_as_argument.html



        "Least Astonishment" and the Mutable Default Argument



        Mutable objects as default arguments behave like a static variable



        And regarding passing JSON as function input, I don't think it is a bad practice by itself unless the function is doing many things on the JSON.



        Ex: If you need to delete/process a particular set of keys in the JSON, you need to pass JSON to the function that does the job.






        share|improve this answer













        Regarding your warning mutable object as default argument



        Please refer the following



        https://docs.quantifiedcode.com/python-anti-patterns/correctness/mutable_default_value_as_argument.html



        "Least Astonishment" and the Mutable Default Argument



        Mutable objects as default arguments behave like a static variable



        And regarding passing JSON as function input, I don't think it is a bad practice by itself unless the function is doing many things on the JSON.



        Ex: If you need to delete/process a particular set of keys in the JSON, you need to pass JSON to the function that does the job.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Nov 27 '18 at 1:49









        KrishnaKrishna

        6021515




        6021515
































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