import sys
from bs4 import BeautifulSoup

html_doc = open(sys.argv[1], mode="r")
html =  html_doc.read()
soup = BeautifulSoup(html, features="lxml")
for link in soup.find_all("a"):
    if "href" in link.attrs.keys():
        if (link['href'].startswith("#")
                and "tabindex" not in link.attrs.keys()
                and "target" not in link.attrs.keys()):
            link['target'] = "_self"
html_doc.close()
html_doc = open(sys.argv[1], mode="w")
print(soup, file=html_doc)
print("File written")