Creating a function with limited number of args in python

Question

I am learning programming, and I am thinking how to improve this code in a more pythonic way.

I have a function with number of arguments. However, any caller of the function can specify the arguments, and depending on the arguments given, I will return the dictionary. The given arguments must be only from the listed arguments.

The code that I have below has so much duplication (I remove carPower, carTime and carLease however it will do the same if/else part) How can I improve this?

def creating_result(my_struct, 
 carColour=None,
 carPrice=None,
 carGas=None,
 carBrand=None,
 carSpeed=None,
 carOwner=None,
 carPower=None,
 carTime=None,
 carLease=None,
 carEngine=None,
 carType=None
 ): 
 if carColour and isinstance(carColour, list):
 my_struct["carColour"] = { "thekey" : carColour}
 elif carColour:
 my_struct["carColour"] = carColour
 if carPrice and isinstance(carPrice, list):
 my_struct["carPrice"] = { "thekey" : carPrice}
 elif carPrice:
 my_struct["carPrice"] = carPrice
 if carGas and isinstance(carGas, list):
 my_struct["carGas"] = { "thekey" : carGas}
 elif carGas:
 my_struct["carGas"] = carGas
 if carBrand and isinstance(carBrand, list):
 my_struct["carBrand"] = { "thekey" : carBrand}
 elif carBrand:
 my_struct["carBrand"] = carBrand
 if carSpeed and isinstance(carSpeed, list):
 my_struct["carSpeed"] = { "thekey" : carSpeed}
 elif carSpeed:
 my_struct["carSpeed"] = carSpeed
 if carEngine:
 my_struct["carEngine"] = carEngine
 if carPrice:
 my_struct["carPrice"] = carPrice
 if carType:
 my_struct["carType"] = carType
 print "my_struct is ", my_struct
if __name__ == "__main__":
 # test 1st caller
 my_dict = {}
 creating_result(my_dict, carPrice=1, carColour="red")
 # test 2nd caller
 my_dict = {}
 creating_result(my_dict, carSpeed="200", carType="SUV", carPrice=300)

In case I can not change the list of arguments of the function above, how can I improve the (if/else) of the function above?

Answer 1

In all programming language, it is better that a function's name is a verb, or start with a verb. In your case, I would use create_result() instead of creating_result().

One this transformation is done, you would think of a better name for this function as it is quite too generic in its meaning. create_car() would be better and more meaningful in your context.

For the parameters you are passing, they should be written following the snake_name convention. Meaning, for example, carColour becomes car_color, carPrice becomes car_price, ... and so on.

More important: Regardless of the purpose of the parameters you are passing to the creating_result() function, their number is quite much which thing should lead to creating a class and use them as instance attributes.

• learningprogramming: Thanks for the comment! especially for the camel case and wrapping this as a class. However maybe I should simplify the question, in the case I can not change the list of args, how can I improve the (if/else) from the given arguments above?
• Billal BEGUERADJ: You are welcome. Many if ... else statements are usually "reduced" by creating a dictionary. There are many posts about that issue on this website (Example)
• NichtJens: I think, in this case, the if ... else blocks come from some misunderstanding of what to put in a dict and why. So, "creating a dictionary" will actually not help here ;) They should be removed all together, I guess.

Answer 2

Your whole code can be rewritten as:

if __name__ == "__main__":
 # test 1st caller
 my_dict = {}
 my_dict.update(carPrice=1, carColour="red")
 print "my_dict is ", my_dict
 # test 2nd caller
 my_dict = {}
 my_dict.update(carSpeed="200", carType="SUV", carPrice=300)
 print "my_dict is ", my_dict

Which seems to be what you actually want :)

Besides the points raised by @Billal already, I don't understand why you are creating dicts that hold one item under the key "thekey". Can you elaborate on the idea behind that? I feel you might have misunderstood something here.

Thinking about this more, maybe it's even simpler and you only want to initialize the dicts like so:

if __name__ == "__main__":
 # test 1st caller
 my_dict = dict(carPrice=1, carColour="red")
 print "my_dict is ", my_dict
 # test 2nd caller
 my_dict = dict(carSpeed="200", carType="SUV", carPrice=300)
 print "my_dict is ", my_dict