Python Strings – Part 4

So far, you’ve learnt:

• Part 1: The basics — quotes, printing, joining, length, and indexes.
• Part 2: Escapes, multi-line strings, and slicing.
• Part 3: String methods for cleaning and transforming text.

Now it’s time for Part 4: String Formatting.

Formatting means combining variables and strings in neat, readable ways. Instead of messy concatenation with +, formatting lets you create sentences that look natural while still including dynamic values like names, numbers, and results from calculations.

The problem with +

At first, you might try joining text with +. This works fine if everything is already text:

first = "Hello"
second = "World"
print(first + " " + second)

But problems appear when you mix in numbers (like ages, scores, or prices).

name = "Alice"
age = 12

# ❌ This will cause an error
print("My name is " + name + " and I am " + age + " years old.")

Why? Because Python won’t automatically convert the number 12 into a string.
You can fix it by converting manually with str(age):

print("My name is " + name + " and I am " + str(age) + " years old.")

This works, but it’s clunky and hard to read. Luckily, Python gives us better ways.

F-strings (the easy way)

F-strings are the most modern and beginner-friendly solution. The idea is simple:

• Put an f right before the quotes.
• Drop variables directly into the string using { }.

name = "Alice"
age = 12
print(f"My name is {name} and I am {age} years old.")

No need to convert numbers or break up the sentence — Python handles it all.

You can even put expressions inside the curly braces:

print(f"Next year I will be {age + 1}")

This makes your output short, clean, and very readable.

Try this

1. Make variables for your name and favourite colour.
2. Print a sentence like: "My name is ___ and my favourite colour is ___."
3. Add a variable for your age and include it in the same sentence.

Using .format()

Before f-strings were introduced, Python used the .format() method. It’s still common in older tutorials and codebases, so it’s worth knowing.

name = "Bob"
age = 20
print("My name is {} and I am {} years old.".format(name, age))

The { } placeholders are replaced by the values you give to .format(), in the same order.

You can also reorder or repeat values using index numbers inside the braces:

print("First: {0}, Second: {1}, First again: {0}".format("A", "B"))

This flexibility is why .format() was popular — but for new learners, f-strings are simpler.

Try this

1. Print "I like apples and oranges" using .format().
2. Swap the order so it prints "I like oranges and apples".

Old-style % formatting

Python also has an older style that uses % signs. You may see it in very old code, but it’s mostly replaced by .format() and f-strings.

name = "Charlie"
age = 15
print("My name is %s and I am %d years old." % (name, age))

Here:

• %s is for strings
• %d is for integers (whole numbers)
• %f is for floating point numbers (decimals)

This style can look confusing, so don’t worry if it feels odd. Just know it exists.

Formatting numbers

Formatting isn’t only for inserting variables — it can also control how numbers appear.

With f-strings you can:

• Round numbers to a set number of decimal places.
• Add commas for large numbers.

Examples:

price = 12.3456
print(f"Price: {price:.2f}")   # Price: 12.35 (rounded to 2 decimal places)

big_number = 1000000
print(f"{big_number:,}")       # 1,000,000 with commas

This is very useful for things like money, scores, and reports, where presentation matters.

Try this

1. Make pi = 3.14159265. Print it rounded to 2 decimal places.
2. Make big = 1234567890. Print it with commas.

Putting it all together

Here’s a short program that uses f-strings to format text and numbers neatly:

name = "Daisy"
score = 97.456
rank = 1

print(f"Congratulations {name}!")
print(f"Your score is {score:.1f} points.")
print(f"You are ranked #{rank:,} in the world!")

Output:

Congratulations Daisy!
Your score is 97.5 points.
You are ranked #1 in the world!

See how much easier it is to read and understand compared to using + everywhere.

Try this

Write a program that:

1. Asks the user for their name and age.
2. Prints: "Hello NAME, next year you will be AGE+1." using an f-string.

Summary

• + works for joining text but is clumsy with numbers.
• F-strings are the modern, easiest way to combine variables and text.
• .format() is older but still useful to recognise.
• % formatting is very old, mostly replaced now.
• F-strings can also format numbers (rounding, commas, etc.).

✅ With string formatting, you can now build clear, professional-looking messages, reports, and outputs in your Python programs.