Notice: This page requires JavaScript to function properly.
Please enable JavaScript in your browser settings or update your browser.Lære Concatenation, Repetition, and Basic Formatting | Strings
Data Types in Python

bookConcatenation, Repetition, and Basic Formatting

You often need to build messages from pieces (names, numbers, results). Python gives you three core tools: + to glue a few strings, * to repeat a string, and f-strings to format values neatly. When joining many pieces (e.g., a list of words), use str.join.

Concatenation with +

Use + to join a small number of strings. If you need to combine text with numbers, convert the number or use an f-string.


              
1234567

            
first = "Hello"
second = "world"
msg = first + " " + second           # "Hello world"

score = 10
# "score: " + score        # TypeError
msg2 = "score: " + str(score)        # OK: "score: 10"
copy

Repetition with *

Multiply a string by an integer to repeat it.


              
12

            
echo = "ha" * 3          # "hahaha"
rule = "-" * 10          # "----------"
copy

Joining many pieces with "sep".join(...)

join is ideal when you have an iterable (like a list) of strings.


              
12345

            
words = ["Python", "is", "fun"]
sentence = " ".join(words)            # "Python is fun"

lines = ["ID: 42", "OK", "Done"]
block = "\n".join(lines)              # "ID: 42\nOK\nDone"
copy

Basic formatting with f-strings

An f-string evaluates expressions inside {} and inserts the result. It’s concise and handles type conversion automatically.


              
123

            
name = "Ada"
tasks = 3
print(f"{name} completed {tasks} tasks.")   # "Ada completed 3 tasks."
copy

Numeric formatting (common cases).


              
1234

            
price = 12.5
tax = 0.2
total = price * (1 + tax)
print(f"Total: {total:.2f}")   # 2 decimal places, e.g., "Total: 15.00"
copy

If you need a literal brace, double it.


              
1

            
print(f"Use {{}} for placeholders.")  # "Use {} for placeholders."
copy
Note
Note

For long loops that build big strings, collect pieces and then ''.join(pieces) (you saw why in the immutability chapter).

1. You have items = ["red", "green", "blue"]. Which is the best way to produce "red, green, blue"?

2. What does "ha" * 2 + "!" produce?

3. Which line prints a price with two decimal places if total = 7.5?

question mark

You have items = ["red", "green", "blue"]. Which is the best way to produce "red, green, blue"?

Select the correct answer

question mark

What does "ha" * 2 + "!" produce?

Select the correct answer

question mark

Which line prints a price with two decimal places if total = 7.5?

Select the correct answer

Var alt klart?

Hvordan kan vi forbedre det?

Tak for dine kommentarer!

Sektion 3. Kapitel 5

Spørg AI

expand

Spørg AI

ChatGPT

Spørg om hvad som helst eller prøv et af de foreslåede spørgsmål for at starte vores chat

Suggested prompts:

Can you explain when to use f-strings versus str.join?

What happens if I try to join non-string elements with join?

Can you show more examples of numeric formatting with f-strings?

Awesome!

Completion rate improved to 5

bookConcatenation, Repetition, and Basic Formatting

Stryg for at vise menuen

You often need to build messages from pieces (names, numbers, results). Python gives you three core tools: + to glue a few strings, * to repeat a string, and f-strings to format values neatly. When joining many pieces (e.g., a list of words), use str.join.

Concatenation with +

Use + to join a small number of strings. If you need to combine text with numbers, convert the number or use an f-string.


              
1234567

            
first = "Hello"
second = "world"
msg = first + " " + second           # "Hello world"

score = 10
# "score: " + score        # TypeError
msg2 = "score: " + str(score)        # OK: "score: 10"
copy

Repetition with *

Multiply a string by an integer to repeat it.


              
12

            
echo = "ha" * 3          # "hahaha"
rule = "-" * 10          # "----------"
copy

Joining many pieces with "sep".join(...)

join is ideal when you have an iterable (like a list) of strings.


              
12345

            
words = ["Python", "is", "fun"]
sentence = " ".join(words)            # "Python is fun"

lines = ["ID: 42", "OK", "Done"]
block = "\n".join(lines)              # "ID: 42\nOK\nDone"
copy

Basic formatting with f-strings

An f-string evaluates expressions inside {} and inserts the result. It’s concise and handles type conversion automatically.


              
123

            
name = "Ada"
tasks = 3
print(f"{name} completed {tasks} tasks.")   # "Ada completed 3 tasks."
copy

Numeric formatting (common cases).


              
1234

            
price = 12.5
tax = 0.2
total = price * (1 + tax)
print(f"Total: {total:.2f}")   # 2 decimal places, e.g., "Total: 15.00"
copy

If you need a literal brace, double it.


              
1

            
print(f"Use {{}} for placeholders.")  # "Use {} for placeholders."
copy
Note
Note

For long loops that build big strings, collect pieces and then ''.join(pieces) (you saw why in the immutability chapter).

1. You have items = ["red", "green", "blue"]. Which is the best way to produce "red, green, blue"?

2. What does "ha" * 2 + "!" produce?

3. Which line prints a price with two decimal places if total = 7.5?

question mark

You have items = ["red", "green", "blue"]. Which is the best way to produce "red, green, blue"?

Select the correct answer

question mark

What does "ha" * 2 + "!" produce?

Select the correct answer

question mark

Which line prints a price with two decimal places if total = 7.5?

Select the correct answer

Var alt klart?

Hvordan kan vi forbedre det?

Tak for dine kommentarer!

Sektion 3. Kapitel 5
some-alt