Lesson 1 — File Recap & First Strings

🎯 Learning Objectives

✓
Open and read a text file line by line using a for loop
✓
Write processed content to an output file
✓
Use .upper() to convert a string to ALL CAPITALS
✓
Use .lower() to convert a string to all lowercase
✓
Understand that strings are immutable — you must store the result

🃏 Match the Terms ACTIVITY 1

Click a term on the left, then click its matching definition on the right.

Matched: 0 / 5

open()

.upper()

.lower()

for loop

.write()

Returns a copy of the string in all lowercase letters

Opens a file and returns a file object to work with

Sends text to an open file

Repeats a block of code for each item in a sequence

Returns a copy of the string in ALL CAPITAL letters

💻 Your First Program ACTIVITY 2

📁 Before you start: Open Notepad and create a file called input.txt. Save it in the same folder where you will save your Python file. Copy the text below and paste it into Notepad, then save the file:

TEXT — input.txt

My Name Is Alex
i love coding in python
GCSE Computer Science Is Fun
hello World
The Quick Brown Fox
jersey is a BEAUTIFUL island

📋 Instructions: Copy the code below into IDLE (File → New File), save it as lesson1.py in the same folder as your input.txt. Run it with F5. Check the output.txt file that is created!

Python — lesson1.py

# ============================================
# Lesson 1 — File Recap & String Case
# ============================================

# --- STEP 1: Open the input file for reading ---
input_file = open("input.txt", "r")

# --- STEP 2: Open the output file for writing ---
output_file = open("output.txt", "w")

# --- STEP 3: Loop through every line in the input file ---
for line in input_file:

    # Remove the newline character from the end of each line
    line = line.strip()

    # Convert the line to UPPER CASE
    upper_line = line.upper()

    # Convert the line to lower case
    lower_line = line.lower()

    # Print both versions to the screen
    print("UPPER:", upper_line)
    print("lower:", lower_line)

    # Write the upper case version to the output file
    output_file.write(upper_line + "\n")

# --- STEP 4: Close both files ---
input_file.close()
output_file.close()

print("\n✅ Done! Check your output.txt file.")

🔬 Now Experiment! CHALLENGES

1
Change line 22 so it writes the lower case version instead of upper case to the file.
2
Add a print("---") after the two print statements so each pair is separated by a line.
3
What happens if you try line.UPPER() instead of line.upper()? Try it and note the error!
4
Add a 3rd variable called title_line using Python's .title() — what does it do?

✏️ Fill in the Blanks ACTIVITY 3

Complete the code below by typing in the missing parts. Press Check when done.

# Open the input file my_file =

for line in my_file:
    line = line.  # clean whitespace
    result = line.  # make ALL CAPS
    print(result)

my_file.

🧠 Quick Quiz ACTIVITY 4

What does "Hello World".upper() return?

Hello World

hello world

HELLO WORLD

Hello WORLD

Which mode string do you use to open a file for writing?

"r"

"w"

"x"

"write"

If name = "Python", what is the value of name after name.lower()?

"python"

"Python" — strings are immutable, lower() returns a new string

"PYTHON"

An error occurs

What is the purpose of .strip() when reading file lines?

It removes all vowels from the string

It removes whitespace and newline characters from both ends

It deletes the line from the file

It converts the line to a list

🔮 Predict the Output ACTIVITY 5

Look at each code snippet and predict what will be printed. Click to reveal the answer!

What does this print?

word = "Python"
print(word.upper())
print(word)

PYTHON
PYTHON

PYTHON
Python

python
Python

An error

What does this print?

text = "Hello World"
result = text.lower()
print(result)

Hello World

hello world

HELLO WORLD

Hello world

What does this print?

name = "jersey"
name.upper()
print(name)

JERSEY

jersey

Jersey

An error

🎮 Memory Game ACTIVITY 6

Match each function to its description. Click two cards to flip them!

Moves: 0Pairs: 0/4

🚀 Extension Activity STRETCH

Challenge: Title Case Converter

Modify your program so that instead of converting lines to upper or lower case, it converts them to title case (first letter of each word capitalised).

Steps:
1. Read each line from input.txt
2. Use Python's .title() method to convert to title case
3. Write the original line AND the title case version to output.txt
4. At the end, print how many lines were processed

Extra challenge: Also write the swapcase version using .swapcase() — what does it do? Find out!