Python File Reading with Loops

Goal

Today you will learn how to:

• Open a text file
• Read data from the file
• Use a loop to read every line
• Convert text into numbers
• Display results neatly

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Part 1: Create Your Text File

Create a file called:

numbers.txt

Put these values inside:

12
25
8
41
19

Save it in the same folder as your Python program.

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Part 2: Read One Line First

Start with this code:

file = open("numbers.txt", "r")

line = file.readline()

print(line)

file.close()

What happens?

✅ It opens the file ✅ Reads only the first line ✅ Prints it

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Part 3: Read Every Line with a While Loop

Now use a loop:

file = open("numbers.txt", "r")

line = file.readline()

while line != "":
    print(line)
    line = file.readline()

file.close()

Important Idea

The loop keeps running until Python reaches the end of the file.

When there are no more lines:

line == ""

That means stop.

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Part 4: Clean Up Extra Spaces

You may notice blank lines appear.

Use .strip():

file = open("numbers.txt", "r")

line = file.readline()

while line != "":
    print(line.strip())
    line = file.readline()

file.close()

Why?

.strip() removes:

• invisible spaces
• enter keys (\n)

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Part 5: Convert Text to Numbers

Everything in a file is read as text.

Convert each line:

file = open("numbers.txt", "r")

line = file.readline()

while line != "":
    number = int(line)
    print(number)
    line = file.readline()

file.close()

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Part 6: Add a Running Total

Now total everything:

file = open("numbers.txt", "r")

total = 0

line = file.readline()

while line != "":
    number = int(line)
    total += number
    line = file.readline()

file.close()

print("Total =", total)

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Challenge 🚀

Can you also find:

• largest number
• smallest number
• average

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Advanced Version (for loop style)

Python can read lines even easier:

file = open("numbers.txt", "r")

for line in file:
    print(line.strip())

file.close()

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Exit Ticket 🎯

Answer:

1. Why do we use line = file.readline() before the loop?
2. What does .strip() do?
3. Why do we convert to int()?

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Bonus Challenge

Create your own file called:

highscores.txt

Add 5 game scores and calculate the total.

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