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?

Billal BEGUERADJ · Accepted Answer · 2017-10-17 18:47:38Z

4

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.

answered Oct 17, 2017 at 18:47

Billal BEGUERADJ

1

\$\begingroup\$ 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? \$\endgroup\$

learningprogramming
– learningprogramming

2017-10-17 18:56:15 +00:00
Commented Oct 17, 2017 at 18:56
\$\begingroup\$ 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) \$\endgroup\$

Billal BEGUERADJ
– Billal BEGUERADJ

2017-10-17 19:07:34 +00:00
Commented Oct 17, 2017 at 19:07
\$\begingroup\$ 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. \$\endgroup\$

NichtJens
– NichtJens

2017-10-17 21:04:43 +00:00
Commented Oct 17, 2017 at 21:04

Add a comment |

NichtJens · Accepted Answer · 2019-11-18 15:58:06Z

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

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