String formatting using f-strings in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of f-string with expressions

What is the output of this Python code?

Python

name = "Alice"
age = 30
print(f"{name} will be {age + 5} years old in 5 years.")

A Alice will be 35 years old in 5 years.

B Alice will be age + 5 years old in 5 years.

C Alice will be 30 + 5 years old in 5 years.

D SyntaxError

💡 Hint

Remember that expressions inside curly braces in f-strings are evaluated.

The expression {age + 5} calculates 30 + 5 = 35, so the output is 'Alice will be 35 years old in 5 years.'

❓ Predict Output

intermediate

Formatting numbers with f-strings

What is the output of this code?

Python

value = 3.14159
print(f"Value rounded to 2 decimals: {value:.2f}")

A Value rounded to 2 decimals: 3.14159

B Value rounded to 2 decimals: 3.14

C Value rounded to 2 decimals: 3.1

D Value rounded to 2 decimals: 3.15

💡 Hint

The format specifier .2f rounds the float to 2 decimal places.

The format specifier .2f rounds the number 3.14159 to 3.14 in the output.

❓ Predict Output

advanced

Using f-string with dictionary values

What will this code print?

Python

person = {"name": "Bob", "age": 25}
print(f"{person['name']} is {person['age']} years old.")

A Bob is 25 years old.

B {person['name']} is {person['age']} years old.

C SyntaxError

D Bob is person['age'] years old.

💡 Hint

You can use dictionary keys inside the curly braces in f-strings.

The f-string evaluates person['name'] as 'Bob' and person['age'] as 25, so it prints 'Bob is 25 years old.'

❓ Predict Output

advanced

Nested f-string expressions

What is the output of this code?

Python

x = 4
print(f"Square of {x} is {x**2} and cube is {x**3}.")

A Square of 4 is 8 and cube is 12.

B Square of x is x**2 and cube is x**3.

C SyntaxError

D Square of 4 is 16 and cube is 64.

💡 Hint

Expressions inside curly braces are evaluated before printing.

x**2 is 16 and x**3 is 64, so the output is 'Square of 4 is 16 and cube is 64.'

❓ Predict Output

expert

Using f-string with alignment and padding

What is the output of this code?

Python

for i in range(1,4):
    print(f"Number: {i:>3}")

A

Number:1
Number:2
Number:3

B

Number: 1
Number: 2
Number: 3

C

Number:  1
Number:  2
Number:  3

D SyntaxError

💡 Hint

The >3 means right-align the number in a space of width 3.

Each number is printed right-aligned in a field 3 characters wide, so there are spaces before the number.

Practice

1. What is the main purpose of using f-strings in Python?

easy

A. To easily insert variables or expressions inside strings

B. To create lists from strings

C. To convert strings to uppercase

D. To repeat strings multiple times

Solution

1. Step 1: Understand f-string usage

   F-strings allow embedding variables or expressions inside strings using curly braces {}.

2. Step 2: Compare options

   Only To easily insert variables or expressions inside strings describes this purpose correctly; others describe unrelated string operations.

3. Final Answer:

   To easily insert variables or expressions inside strings -> Option A

4. Quick Check:

   f-strings = insert variables in strings [OK]

Hint: Remember: f-strings embed variables with curly braces {} [OK]

Common Mistakes:

• Confusing f-strings with string methods like upper()
• Thinking f-strings create lists
• Assuming f-strings repeat strings

2. Which of the following is the correct syntax to use an f-string to insert variable name into a string?

easy

A. "Hello, $name!"

B. f"Hello, {name}!"

C. f'Hello, $name!'

D. "Hello, {name}!"

Solution

1. Step 1: Identify f-string syntax

   An f-string starts with the letter f before the quotes and uses curly braces {} to insert variables.

2. Step 2: Check each option

   f"Hello, {name}!" correctly uses f"Hello, {name}!". Options A and B lack the f prefix, and C uses incorrect syntax with $name.

3. Final Answer:

   f"Hello, {name}!" -> Option B

4. Quick Check:

   f-string = f"text {var}" [OK]

Hint: f-string must start with f and use {variable} inside quotes [OK]

Common Mistakes:

• Omitting the f before the string
• Using $ instead of curly braces
• Using single quotes without f prefix

3. What will be the output of this code?

name = "Alice"
age = 30
print(f"{name} is {age} years old.")

medium

A. name is age years old.

B. {name} is {age} years old.

C. SyntaxError

D. Alice is 30 years old.

Solution

1. Step 1: Evaluate variables inside f-string

   The variables name and age are replaced by their values "Alice" and 30 inside the string.

2. Step 2: Understand print output

   The print statement outputs the string with variables replaced: "Alice is 30 years old.".

3. Final Answer:

   Alice is 30 years old. -> Option D

4. Quick Check:

   f-string replaces {name} and {age} with values [OK]

Hint: f-string prints variable values, not variable names [OK]

Common Mistakes:

• Expecting curly braces to print literally
• Confusing variable names with values
• Thinking f-string causes syntax error here

4. Find the error in this code snippet:

age = 25
print(f"Age is {age")

medium

A. Missing closing brace '}' in f-string

B. Missing f before the string

C. Variable age is not defined

D. Incorrect use of quotes

Solution

1. Step 1: Check f-string braces

   The f-string has an opening brace { but no matching closing brace }, causing a syntax error.

2. Step 2: Verify other parts

   The f prefix is present, variable age is defined, and quotes are correct.

3. Final Answer:

   Missing closing brace '}' in f-string -> Option A

4. Quick Check:

   Every { must have a matching } in f-string [OK]

Hint: Count braces in f-string; each { needs a } [OK]

Common Mistakes:

• Forgetting to close curly braces
• Thinking missing f causes this error
• Assuming variable is undefined

5. You want to print the price of an item with 2 decimal places using f-strings. Which code correctly formats the price variable?

price = 9.8765
# Choose the correct print statement

hard

A. print(f"Price: ${price:2f}")

B. print(f"Price: ${price:.2}")

C. print(f"Price: ${price:.2f}")

D. print(f"Price: ${price:.2d}")

Solution

1. Step 1: Understand format specifier for decimals

   To format a float with 2 decimal places, use :.2f inside the curly braces.

2. Step 2: Check each option

   print(f"Price: ${price:.2f}") uses {price:.2f} correctly. print(f"Price: ${price:2f}") misses the dot, print(f"Price: ${price:.2}") misses the type specifier, and print(f"Price: ${price:.2d}") uses invalid d for decimals.

3. Final Answer:

   print(f"Price: ${price:.2f}") -> Option C

4. Quick Check:

   Use :.2f to format float with 2 decimals [OK]

Hint: Use :.2f inside {} to show 2 decimal places [OK]

Common Mistakes:

• Omitting the dot before precision
• Using integer format 'd' for floats
• Leaving out the type specifier