Why creating a variable and using that variable as reference can lead to confusion?

Introduction

In a Python script, I wanted to test different HTML strings using the same logic. My approach was to loop through a range to create multiple instances of the HTML string variables, but it wasn't working as expected.

# DO NOT DO THIS

for i in range(1, 5):
    html = f"html{i}"
    soup = BeautifulSoup(html, "html.parser")
    print('----', soup)

The behavior I was observing is due to the way the formatted string f"html{i}" is interpreted. In my code, f"html{i}" evaluates to the literals "html1", "html2", "html3", and "html4" rather than the contents of variables named html1, html2, etc.

Python does not automatically replace f"html{i}" with the value of the variable whose name is dynamically created such as html1 or html2. Instead, it evaluates the string as a fixed pattern comprised of the prefix "html" followed by the value of i.

If I want to use the contents of pre-defined variables html1, html2, etc., I need to explicitly retrieve their values, for example using a dictionary to map string names to their actual content.

Here's an example illustrating this:

from bs4 import BeautifulSoup

# Define the variables
html1 = "Test 1"
html2 = "Test 2"
html3 = "Test 3"
html4 = "Test 4"

# Store them in a dictionary for easy access
html_dict = {
    "html1": html1,
    "html2": html2,
    "html3": html3,
    "html4": html4
}

# Iterate and process each html content
for i in range(1, 5):
    key = f"html{i}"
    html = html_dict[key]
    soup = BeautifulSoup(html, "html.parser")
    print('----', soup)

Explanation:

1. Define Variables:

   • html1, html2, html3, html4 are defined with the content you want to parse.

2. Dictionary for Variable Lookup:

   • html_dict is created to map the string names to their corresponding contents.

3. Iterate Over Keys:

   • The loop generates the keys "html1" to "html4".
   • key = f"html{i}" constructs the key.
   • html = html_dict[key] retrieves the content associated with the key.

4. Parse and Print:

   • Parses the HTML content using BeautifulSoup.
   • Prints the parsed content.

Output:

---- Test 1
---- Test 2
---- Test 3
---- Test 4

This approach dynamically accesses the content of the variables based on the iteration index and correctly prints the intended content.