Question

New to python-can someone tell me what I am doing wrong?

I need to write a function that takes unknown number of arguments and returns a unique list.
For example:

a= ['mary', 'james', 'john', 'john']
b= ['elsie', 'james', 'elsie', 'james']

unique_list(a,b)

['mary', 'james','john', 'elsie']

This is some of the code I have after doing some research but the output is not what I need:

def unique_list:(*something)
    result1= list(something)
    result = ' '.join(sum(result1, []))
    new= []
    for name in result:
            if name not in new:
                           new.append(name)
    return new

       
>>> unique_list(a,b)
['m', 'a', 'r', 'y', ' ', 'j', 'e', 's', 'o', 'h', 'n', 'l', 'i']

This is another one I have tired:

def unique_list(*something):
    result= list(something) 
    new=[]
    for name in result:
        if name not in new:
            new.append(name)
    return new

>>> unique_list(a,b)
[['mary', 'james', 'john', 'john'], ['elsie', 'james', 'elsie', 'james']]

Another one but I got an error message:

def single_list(*something):
    new=[]
    for name in something:
        if name not in new:
            new.append(name)
    new2= list(set(new))
    return new2

>>> single_list(a,b)
Traceback (most recent call last):
  File "", line 1, in 
    single_list(a,b)
  File "", line 6, in single_list
    new2= list(set(new))
TypeError: unhashable type: 'list'

Any ideas? Thank you in advance for all your help.

Answer 1

You can concatenate all the lists and then create a set from this resulting list. This will work for any number of passed in lists where the function looks like def unique_lists( *lists )

ret_list = []
for l in lists:
    ret_list = ret_list + l

return set( ret_list )