How to create a function in Python that makes objects (i.e lists)

Question

I couldn't find a guide that would help me out in this area. So I was hoping somebody could help me explain this kind of programming in Python. I am trying to write a code that goes something like this:

def Runner():
    for G in range(someRange):
        makeListObjectcalled 'ListNumber'+'G'
        ListNumberg.append(G*500000 or whatever)
        print ListNumberG 
    #so I would have a someRange amount of lists 
    #named 0,1,2,3...(up to someRange) I could look through

I think it can be done with classes (in fact I'm guessing thats what they're for...) but I'm not sure. Could someone lay me down some clarifications please?

The most important question is why do you think you need to do it this way, and what do the names mean? For that reason, giving more context might help. Either of wez's answer or Eric Finn's answer might be right, depending on that. If the names are meaningful, use the dictionary. If you just need a bunch of different lists, (or lists in a particular order), use the list of lists solution Eric gave. — Justin Blank
– Justin Blank, Commented Jun 5, 2012 at 15:58

Eric Finn · Accepted Answer · 2012-06-05 15:54:39Z

1

It looks like what you really want is a list of lists.

def Runner():
    Lists = []
    for G in range(someRange):
        Lists[G] = []
        Lists[G].append(G*500000 or whatever)
        print Lists[G]
        #This way, you have Lists[0], Lists[1], ..., Lists[someRange]

answered Jun 5, 2012 at 15:54

Eric Finn

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1 Comment

Valentine Bondar Over a year ago

Indeed! I couldn't exactly point my finger on how to summarize it in one simple step. Thank you loads!

invert · Accepted Answer · 2012-06-05 14:18:45Z

1

You want to dynamically create variables of type lists that store an array of values.

An easier and better approach (than juggling unknown variable names) is to use a dictionary to keep your lists in, so you can look them up by name/key:

(pseudo code, don't have my Python interpreter with me)

# create a dictionary to store your ListNumberG's
dict_of_lists = {}

# down the line in your loop, add each generated list to the dict:
dict_of_lists['ListNumberG'] = ListNumberG

Later you can find a list by it's name/key via

print(dict_of_lists['ListNumberG'])

or loop through them

for idx in range(bestguess):
    print(dict_of_lists['ListNumber%s' % (idx,)])

answered Jun 5, 2012 at 14:18

invert

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1 Comment

Valentine Bondar Over a year ago

This actually helped me on another problem I was working on, thank you big time Wez. You've just made my day immensely productive ^.^

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