How to filter through a defaultdict?

I have a CSV input file that I organized as a defaultdict:

{
 '1234' : [('1,60', 'text', 'supplier1')],
 '3456' : [('1,98', 'another text', 'supplier2')],
 ['1,54', 'text again', 'supplier1'],
 '709' : [('2,90', 'again', 'supplier2')] 
}

I would like to is prioritize tuples containing "supplier1". If there are results for the same key for supplier1 and 2, keep only supplier1. And if no results for a given key for supplier1, keeping results with other suppliers.

EDIT : desired output :

{
 '1234' : [('1,60', 'text', 'supplier1')],
 '3456' : ['1,54', 'text again', 'supplier1'],
 '709' : [('2,90', 'again', 'supplier2')] 
}

As defaultdict is a subclass of dict, we can assume a regular dictionary of lists (at the same time, I've fixed some syntax errors which I assume are typos):

d = {'1234' : [('1,60', 'text', 'supplier1')],
     '3456' : [('1,98', 'another text', 'supplier2'),
               ('1,54', 'text again', 'supplier1')],
     '709' :  [('2,90', 'again', 'supplier2')]}

You can then use a dictionary comprehension with a custom function to perform your task:

def get_data(x):
    for tup in x:
        if tup[-1] == 'supplier1':
            return [tup]
    return x

res = {k: get_data(v) for k, v in d.items()}

{'1234': [('1,60', 'text', 'supplier1')],
 '3456': [('1,54', 'text again', 'supplier1')],
 '709':  [('2,90', 'again', 'supplier2')]}