Lära Konkatenering, Upprepning och Grundläggande Formatering

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.


              1234567891011
            
# Creating a personalized game message
player_first = "Alice"
player_last = "Johnson"
greeting = player_first + " " + player_last  # "Alice Johnson"

score = 10
# "Score: " + score  # TypeError → number must be converted to string
score_message = "Score: " + str(score)       # "Score: 10"

print(greeting)
print(score_message)

Repetition with `*`

Multiply a string by an integer to repeat it.


              12345
            
echo = "ha" * 3          # "hahaha"
rule = "-" * 10          # "----------"

print(echo)
print(rule)

Joining Many Pieces with `"sep".join(...)`

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


              123456789
            
# Building a message and a log entry from list data
message_parts = ["Welcome", "to", "Codefinity!"]
welcome_message = " ".join(message_parts)  # "Welcome to Codefinity!"

log_lines = ["User ID: 42", "Status: OK", "Process: Done"]
log_block = "\n".join(log_lines)           # "User ID: 42\nStatus: OK\nProcess: Done"

print(welcome_message)
print(log_block)

Basic Formatting with `f-strings`

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


              1234
            
# Displaying a progress message for a team member
name = "Ada"
tasks = 3
print(f"{name} completed {tasks} tasks.")   # "Ada completed 3 tasks."

Numeric formatting (common cases).


              123456
            
# Calculating the total cost of an online purchase
item_price = 12.5
tax_rate = 0.2
total_cost = item_price * (1 + tax_rate)

print(f"Total to pay: ${total_cost:.2f}")  # Rounded to 2 decimal places, e.g. "Total to pay: $15.00"

If you need a literal brace, double it.


              1
            
print(f"Use {{}} for placeholders.")  # "Use {} for placeholders."

Note

For long loops that build big strings, collect pieces and then ''.join(pieces).

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 5

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Fråga vad du vill eller prova någon av de föreslagna frågorna för att starta vårt samtal

Suggested prompts:

Can you explain when to use each string operation in practice?

What are some common mistakes to avoid with string concatenation and formatting?

Can you show more examples of f-string formatting, especially with numbers?

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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.


              1234567891011
            
# Creating a personalized game message
player_first = "Alice"
player_last = "Johnson"
greeting = player_first + " " + player_last  # "Alice Johnson"

score = 10
# "Score: " + score  # TypeError → number must be converted to string
score_message = "Score: " + str(score)       # "Score: 10"

print(greeting)
print(score_message)

Repetition with `*`

Multiply a string by an integer to repeat it.


              12345
            
echo = "ha" * 3          # "hahaha"
rule = "-" * 10          # "----------"

print(echo)
print(rule)

Joining Many Pieces with `"sep".join(...)`

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


              123456789
            
# Building a message and a log entry from list data
message_parts = ["Welcome", "to", "Codefinity!"]
welcome_message = " ".join(message_parts)  # "Welcome to Codefinity!"

log_lines = ["User ID: 42", "Status: OK", "Process: Done"]
log_block = "\n".join(log_lines)           # "User ID: 42\nStatus: OK\nProcess: Done"

print(welcome_message)
print(log_block)

Basic Formatting with `f-strings`

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


              1234
            
# Displaying a progress message for a team member
name = "Ada"
tasks = 3
print(f"{name} completed {tasks} tasks.")   # "Ada completed 3 tasks."

Numeric formatting (common cases).


              123456
            
# Calculating the total cost of an online purchase
item_price = 12.5
tax_rate = 0.2
total_cost = item_price * (1 + tax_rate)

print(f"Total to pay: ${total_cost:.2f}")  # Rounded to 2 decimal places, e.g. "Total to pay: $15.00"

If you need a literal brace, double it.


              1
            
print(f"Use {{}} for placeholders.")  # "Use {} for placeholders."

Note

For long loops that build big strings, collect pieces and then ''.join(pieces).

Var allt tydligt?

Tack för dina kommentarer!

Avsnitt 3. Kapitel 5

Konkatenering, Upprepning och Grundläggande Formatering

Concatenation with `+`

Repetition with `*`

Joining Many Pieces with `"sep".join(...)`

Basic Formatting with `f-strings`

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`?

Konkatenering, Upprepning och Grundläggande Formatering

Concatenation with `+`

Repetition with `*`

Joining Many Pieces with `"sep".join(...)`

Basic Formatting with `f-strings`

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`?

Konkatenering, Upprepning och Grundläggande Formatering

Concatenation with +

Repetition with *

Joining Many Pieces with "sep".join(...)

Basic Formatting with f-strings

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?

Konkatenering, Upprepning och Grundläggande Formatering

Concatenation with +

Repetition with *

Joining Many Pieces with "sep".join(...)

Basic Formatting with f-strings

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?

Concatenation with `+`

Repetition with `*`

Joining Many Pieces with `"sep".join(...)`

Basic Formatting with `f-strings`

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`?

Concatenation with `+`

Repetition with `*`

Joining Many Pieces with `"sep".join(...)`

Basic Formatting with `f-strings`

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`?