How to specify function calls

[FlyingCatCreatures]

Please excuse me in advance if I inadequately describe the question I have.

I'm trying to load a dataset using numpy, using something like
dataset = np.loadtxt(dataPath, delimiter=',')
The problem here is that I seem to not be able to specify the delimiter like this in the function.

The same problem arises when I use the pd.DatafFrame method like this:
pd.DataFrame(data, columns=["prices"])
Here I cannot specify in the function call 'columns = ["prices"] because it gives the error "Invalid call to 'call': unexpected keyword argument: 'columns'"

Is there any way to specify an optional variable in a function you are calling like this?