Question

So I have a database with 10 fields(call them a, b, c….j), and I need to create a function “find_use()” that can find and modify records in the database based on any combination of fields given to it as arguments ( ie: find_use(a==”happy”, g ==”birthday”) ). Also, due to privileges, I am not generating the SQL queries directly, but instead use an SQL wrapper the system provides called “selector()” which will locate records based on the same arguments, ie: query = selector(a==”happy”, g==”birthday”), which would then return a list of the matching records

So the problem is, since I don’t know what arguments find_use() will be receiving, I don’t know how to structure the inner call to selector(). Ideally, the call to selector should be created dynamically; something to the effect of:

def find_use(a='',b='',c='',.....j=''):
   vars = locals()
   for v in vars:
      if v.value() != '':
        q_string += '{0} == {1},'.format(v.key(),v.value())
   query = selector(q_string) 
   ...do something to query...

This, however, will not work since selector does not take a string, but rather arguments in the same format as the find_use() function. How, then, can this be done. I have the feeling this is actually really easy, and I’m just missing something obvious. Any input would be greatly appreciated.

Answer 1

I think you are looking for keyword argument unpacking:

def find_use(**kwargs):
   query = selector(**kwargs) 
   ...do something to query...

When defined this way, find_use can receive an arbitrary number of keyword arguments. The keyword arguments are collected in a dict, kwargs.

For example,

def foo(**kwargs):
    print(kwargs)    
foo(a = 'happy', g = 'birthday')

yields

{'a': 'happy', 'g': 'birthday'}

and if

def bar(a, g):
    print(a)
    print(g)

then

bar(**{'a': 'happy', 'g': 'birthday'})  # like selector(**kwargs)

yields

happy
birthday