def parse_filenames_and_sizes(list_file):
    """
    Takes a file with tab-delimited filename/size pairs and returns a 
    filename-->size dict.
    """
    
    filename_to_size = {}
    
    with open(list_file,'r') as f:
        
        for line in f:
            if ('catalog.json' in line) or ('stac.json' in line):
                continue
            tokens = line.split('\t')
            assert len(tokens) == 2
            fn = tokens[0]            
            size_str = tokens[1]
            size = int(size_str)
            if size == 0:
                continue
            filename_to_size[fn] = size
            
        # ...for each line
        
    # ...with open()        

    return filename_to_size