Add word or words to dictionary file in txt-format

add_to_dict.py

import sys
import re
import os

add_mode = sys.argv[1]

if add_mode == '--word':
    words = [sys.stdin.read().strip()]
elif add_mode == '--words':
    split_pattern = r'[\ \,\.\:\;\!\?\(\)\{\}\[\]\\\/\|\<\>\$\%\*]+'
    words = re.split(split_pattern, sys.stdin.read())
    words = [w.strip().lower() for w in words]
    words = [w for w in words if w]

    unique_linked_words = []
    for w in words:
        if w not in unique_linked_words:
            unique_linked_words.append(w)

    words = unique_linked_words

print(repr(words))

dict_filepath = sys.argv[2]

if not os.path.isfile(dict_filepath):
    with open(dict_filepath, 'w') as f:
        pass

with open(dict_filepath, 'r+b') as f:

    # add '\n' to end file if need
    f.seek(0, os.SEEK_END)
    if f.tell() != 0:
        f.seek(-1, os.SEEK_END)
        if f.read() != b'\n':
            f.write(b'\n')

    # write words
    for w in words:
        print(w)
        f.write(w.encode())
        f.write(b'\n')

# /Users/dmitryoleynik/Library/Services/add word to dict.workflow
# /usr/local/bin/python3.7 /Users/dmitryoleynik/Library/Services/add_to_dict.py --word /Users/dmitryoleynik/new_words.txt

# /Users/dmitryoleynik/Library/Services/add words to dict.workflow
# /usr/local/bin/python3.7 /Users/dmitryoleynik/Library/Services/add_to_dict.py --words /Users/dmitryoleynik/new_words.txt