gistfile1.txt

data.txt:
------------------------------
<h1>1</h1> <!-- Level One -->
<h4>1.1</h4> <!-- Level Two -->
    <div class='x'>1.1.1</div> <!-- Level Three -->
    <div class='x'>1.1.2</div>
    <div class='x'>1.1.3</div>
    <div class='x'>1.1.4</div>
<h4>1.2</h4>
    <div class='x'>1.2.1</div>
    <div class='x'>1.2.2</div>
    <div class='x'>1.2.3</div>
    <div class='x'>1.2.4</div>
<h4>1.3</h4>
    <div class='x'>1.3.1</div>
    <div class='x'>1.3.2</div>
    <div class='x'>1.3.3</div>
    <div class='x'>1.3.4</div>
<h4>1.4</h4>
    <div class='x'>1.4.1</div>
    <div class='x'>1.4.2</div>
    <div class='x'>1.4.3</div>
    <div class='x'>1.4.4</div>
<h1>2</h1>
<h4>2.1</h4>
    <div class='x'>2.1.1</div>
    <div class='x'>2.1.2</div>
    <div class='x'>2.1.3</div>
    <div class='x'>2.1.4</div>
<h4>2.2</h4>
    <div class='x'>2.2.1</div>
    <div class='x'>2.2.2</div>
    <div class='x'>2.2.3</div>
    <div class='x'>2.2.4</div>
<h4>2.3</h4>
    <div class='x'>2.3.1</div>
    <div class='x'>2.3.2</div>
    <div class='x'>2.3.3</div>
    <div class='x'>2.3.4</div>
<h4>2.4</h4>
    <div class='x'>2.4.1</div>
    <div class='x'>2.4.2</div>
    <div class='x'>2.4.3</div>
    <div class='x'>2.4.4</div>
----------------------


from bs4 import BeautifulSoup

with open('data.txt') as f:
    html = f.read()

soup = BeautifulSoup(html)
elmt = soup.find('h1')
h1_text = elmt.text
 
while True:
    elmt = elmt.next_sibling
    if not elmt: break  #then no more tags

    tag_name = getattr(elmt, 'name', None)  #Tags have names like 'h1', 'h4', 'div'. If the tag 
                                            #does not have a name, e.g. a Comment, return None
    if not tag_name: continue  #Skip the Comment's in your html
    
    if tag_name == 'h1':
        h1_text = elmt.text
    elif tag_name == 'h4':
        h4_text = elmt.text
    elif tag_name == 'div':
        print("{}:{}:{}".format(h1_text, h4_text, elmt.text))