INFO 153 Assignment 1 (10 points)

Objectives

Please solve the following problem with Python programming using proper data structures.

Create a Jupyter Notebook with code and markdown descriptions;
Test your code and make sure it works properly;
Submit your Jupyter Notebook (.ipynb) to blackboard.

A similar application to the parentheses matching problem is HTML (hypertext markup language) validation. In HTML, tags exist in both opening and closing forms and must be balanced to properly describe a web document.

This simple HTML code (string) here:

<html>
<head>
<title>
Example>
</title>
</head>
<body>
<h1>
Hello, world
</h1>
</body>
</html>

shows the matching and nesting structure for tags in the language.

Please create a Jupyter notebook and write a Python program that can validate HTML code with proper opening and åclosing tags. To simplify the problem, we suppose the opening and closing tags are provided in separate lines without indentation (as shown in the above example).

Consult the example on the math checker (parentheses matching) in lecture slides/notes:

http://keensee.com/pdp/python/python_data_structures.html

0. Academic Honesty Statement

Please put the Academic Honesty Statement with your full name printed on your notebook.

Your submission will not be graded without the statement.

1. Create a Stack abstract data type (2 points)

The Stack class should include the following methods:

push(item) function to add a new item to the stack
pop() function to remove and return the top item from the stack
peek() to return the top item in the stack
is_empty() to test whether the stack is empty
size() to tell the size (number of items) in the stack

class Stack: 
    """
    The Stack class to be implemented. 
    Please define all required methods 
    within the class structure. 
    """

2. Create a check_html function (5 points)

def check_html(html_string):
    """Validates an HTML string (text)
    Arguments: 
        html_string (string): the HTML string with tags in each line (separated by \n)
        
    Returns: 
        bool: True if the HTML tags are balanced; False if otherwise. 
    """

Here is what the function should do:

Create a balanced variable and set its initial value to True
Create a new Stack object;
Use the split() method of a string to split it into text lines;
Create a loop to read each text line:
- You can use a for loop such as --
```
for line in text_lines:
```
- If the text line matches an opening tag (e.g. <h1>), add the tag name (e.g. "h1") to the stack;
  - You can use expressions such as "<" in line to check if the symbol "<" appears in the string variable
  - You should make sure "<" is in the text line AND "/" is NOT in it for an openning tag;
  - Use the logical and operator to connect multiple logical conditions;
  - Use statements such as tag_name = line.replace("<","") to remove special symbols, so you can reduce it to its tag name only;
- If the text line is a closing tag (e.g. </h1>), check whether the stack is empty:
  - The HTML code is unbalanced if stack is currently empty:
    - Please use the is_empty() method of the stack object.
  - If not empty, use the stack object's pop() to read and remove the top (last) item from stack:
    - Again, use the replace() method of the text line string variable to remove symbols </>, to reduce it to its tag name only;
    - If the top (last) tag matches (==) the current closing tag, then the HTML code is balanced (True);
    - Otherwise, the HTML code is unbalanced (False).
- If the text line is ordinary content without a HTML tag, skip the line;
  - You do not actually need to do anything in this case.
After the loop, check:
- If the Stack is empty (balanced out), return the value of the balanced variable
- Otherwise, return False

3. Function Calls (0.5 point)

Create two string variables, one with balanced HTML code and the other with unbalanced HTML code.

Call the html_checker() function twice in your code, each time with each of the two variables as argument to test the program. For example:

str1 = "(Valid/balanced HTML code here)"
str2 = "(Invalid/unbalanced HTML code here)"
print("Is the first string valid?", check_html(str1))
print("Is the second string valid?", check_html(str2))

Is the first string valid? None
Is the second string valid? None

You can use the syntax in the box here to create a string with multiple lines.

4. Markdown and Comments (2 point)

Besides your Python code, you should also have:

Markdown headers and text to provide basic descriptions of your work
Comments in the Python code for each function and major step in the code

Bonus (+1 point)

Create a loop to read user input for multiple lines of HTML code (until the user enters an empty line to signal the end) and run the check_html() function to validate the entered HTML.

Important Notes

Do NOT copy and paste other people's code without understanding it and proper acknowledgment.
Make sure your code runs properly before submitting it.
The grade will be significantly penalized if code does NOT work.
Get in touch with the instructor if you need guidance / assistance.