Lesson 5 — Combining It All

🎯 Learning Objectives

✓
Combine upper(), lower(), len(), find(), isalpha(), isdigit() in one program
✓
Apply string processing to a real file-based pipeline
✓
Write a complete, working Python program independently
✓
Debug your own code using error messages

s.upper()

Returns string in ALL CAPS

s.lower()

Returns string in all lowercase

len(s)

Returns number of characters

s.find("x")

Returns index of "x" or -1

s[0]

First character (index 0)

s[-1]

Last character

s[0:3]

Characters at index 0, 1, 2

s.isalpha()

True if ALL letters

s.isdigit()

True if ALL digits

s.isspace()

True if all whitespace

"x" in s

True if "x" is in s

s.strip()

Remove leading/trailing whitespace

TEXT — input.txt

Python is a versatile language
Jersey has a population of 103000
GCSE Computer Science exam is 1CP2
I scored 95 percent on my test
the quick brown fox jumps
Programming helps solve problems
My postcode is JE2 3AB
There are 365 days in a year
Hello World
Channel Islands include Jersey and Guernsey
Room 101 is down the corridor
abcdefghijklmnopqrstuvwxyz

TASK 01

📊 Line Statistics

Write a program that reads every line and writes to output.txt a report showing each line's: original text, length, first character, last character, and an uppercase version. Format it clearly.

Opens input.txt and output.txt correctly

Uses len(), [0], [-1], and .upper() on each line

Writes formatted results to output.txt

Closes both files at the end

Use an f-string: output_file.write(f"Line: {line} | Len: {len(line)} | First: {line[0]}\n")

Structure: open both files → for line in input: strip, process, write → close both

TASK 02

🔍 Keyword Search

Extend your program (or write a new one) that searches each line for a keyword that the user types. Only write lines containing that keyword to output.txt. Print how many matches were found. Make the search case-insensitive.

Uses input() to get the keyword from the user

Converts both line and keyword to lower before comparing

Counts and prints the number of matching lines

Convert both: if keyword.lower() in line.lower():

TASK 03

📈 Character Analyser

Write a program that reads the file and for each line counts: number of letters, number of digits, number of spaces. Write a summary line to output.txt for each line. At the end print totals across the whole file.

Uses a for ch in line inner loop

Uses isalpha(), isdigit(), isspace() correctly

Prints grand totals at the end

Before the outer for loop, set: total_letters = 0, then inside the loop add: total_letters += letters

TASK 04

🔧 Refactor with Subroutines

Take your Task 03 code and refactor it to use subroutines. Create at least two functions:

1. def count_chars(line) — takes a string, returns the count of letters, digits, and spaces
2. def format_report(line, letters, digits, spaces) — takes the data and returns a formatted string for the output file

Defines a count_chars() function that returns multiple values

Defines a format_report() function that returns a formatted string

Main program calls both functions inside the loop

Program produces the same output as Task 03 but with cleaner code

In Python you can return multiple values: return letters, digits, spaces and unpack them: l, d, s = count_chars(line)

Use an f-string: return f"Line: {line} | Letters: {letters} | Digits: {digits} | Spaces: {spaces}\n"

This code has 5 bugs. Find them all — no clue which lines they're on this time. Click underlined text to fix.

input_file = open("input.txt", "a") output_file = open("output.txt", "w") total = 0 for line in input_file: line = line.strip letters = 0 for ch in line: if ch.isalpha(): letters = 1 total += letters if letters < 5: result = upper(line) output_file.write(result + "\n") print("Total letters:", total) input_file.close() output_file.close()

What does this print?

def count_chars(text):
    letters = 0
    digits = 0
    for ch in text:
        if ch.isalpha(): letters += 1
        elif ch.isdigit(): digits += 1
    return letters, digits

l, d = count_chars("Hi 42!")
print(f"{l} letters, {d} digits")

2 letters, 2 digits

3 letters, 2 digits

2 letters, 1 digits

5 letters, 0 digits

TASK 05 — EXTENSION

Challenge: Text Statistics Dashboard

Write a complete program using at least 3 subroutines that produces a detailed text statistics report. Your program should include:

1. def count_chars(line) — counts letters, digits, spaces
2. def find_longest_word(line) — finds the longest word in a line (hint: use .split())
3. def generate_summary(total_lines, total_letters, total_digits, longest_line) — returns a formatted summary string

Read input.txt and write a full report to output.txt. The report should include per-line stats AND an overall summary at the end with totals and the longest line found.

Defines and uses at least 3 subroutines

Reads from input.txt and writes to output.txt

Produces per-line statistics

Produces an overall summary with totals

Split the line into words: words = line.split(). Then loop through and compare lengths: if len(word) > len(longest): longest = word

Combining It All