def remove_list_duplicates(some_list):
    '''returns a new list that has all the duplicates removed'''
    return list(set(some_list))


def find_duplicates(some_list):
    '''returns a set of the numbers that appear at least twice
    in some_list.
    
    Try using two sets: one for all the numbers and one for 
    the duplicates (along with a loop).'''
    
    elem_set = set()    # all the elements in the list
    dups_set = set()    # just the duplicates
    
    for num in some_list:
        if num in elem_set:
            # check if we've already seen num
            dups_set.add(num)
        else:
            # first time we've seen num
            elem_set.add(num)
    
    return dups_set


def count_beans(filename):
    '''Return a list giving the number of beans of each color
    recorded in filename.
    Each entry in the list is a two-element list of
    the bean color and the number of occurrences of that color.'''
    color_counts = []
    data_file = open(filename)
    
    for line in data_file:
        color = line.strip() # throw away the ending newline (\n)
        
        color_found = False # whether I've located the right color
        
        # look through color_counts for color
        for entry in color_counts:
            # check if the color of entry is the right one
            if entry[0] == color:
                # this is the color we want, increment counter
                entry[1] += 1
                color_found = True
                
        if not color_found:
            # we didn't find the right color; this is the
            # first bean of this color -> add a new entry to list
            color_counts.append([color, 1])
            
    data_file.close()
    return color_counts