python 3 - instantiating class from user input

[Brad Bailey]

I dont understand why this is such a big deal. Nor do i understand why google can't find a reasonable answer. If one can't figure out from the title what I'm trying to do, then a look at code should firmly plant the intent. The general idea of the code is, in my opinion, very basic. 

I notice, that when you are coding a class instance, it's in the format of:
newInstance = someClass()

OK, so we are calling someClass as if it's a function. Is there a way to do something to the effect of:
 someClass(newInstance)

I've seen all kinds of hacks and workarounds that seem 10 times more complicated that this ought to be. 

class inventoryItem:
    itsDecrtiption = None
    itsVendor = None
    itsCost = None
    itsMarkup = None
    itsQuantity = None

newItem = input('enter the new item to add to inventory')
findItem = input('enter the item number to find')

def addItem(newItem):
    pass

def lookupItem(findItem):
    if findItem:
        doSomething()
    else:
        complain()
        addItem(findItem)