def evens(the_list):
    '''evens(list) -> list/boolean
    
    Given a list, returns a new list consisting only of those elements with
    an even index. Returns False if the parameter given is not a list.'''
    
    if ( type(the_list) != list ):
        return False
    
    new_list = []
    
    for index in range(0, len(the_list)):
        if ( index % 2 == 0 ):
            new_list.append(the_list[index])
    
    return new_list

def cat(text_file):
    '''cat(file) -> Boolean
    
    Opens and displays a given text file on screen, line by line. Returns False
    if the parameter given is not a file.'''
    
    if ( type(text_file) != file ):
        return False
    
    for line in text_file:
        # Since python also prints out the carriage return at the end of each
        # line of the file, there is no need for us to print out another one
        # of our own.
        print line,
    
    # Just to make it look neat at the end. Otherwise the console gets a bit
    # messy looking.
    print ''

def double_my_digits(input):
    '''double_my_digits(str) -> str/boolean
    
    Given a string consisting only of numbers, will return a string obtained by
    doubling each digit in the input string. Will return False if the input is
    not a string, or contains something other than what is allowed in an int.'''
    
    if ( type(input) != str ):
        return False
    
    try:
        input = int(input)
    except ValueError:
        return False
    
    input = str(input)
    new_string = ''
    for digit in input:
        new_string += str(int(digit) * 2)
        
    return new_string