Formatting using format() method in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of positional and keyword arguments in format()

What is the output of this code snippet?

Python

result = "{1} scored {score} points".format("Alice", "Bob", score=95)
print(result)

A Bob scored 95 points

B Alice scored 95 points

C 1 scored 95 points

D IndexError

💡 Hint

Remember that numbers inside curly braces refer to positional arguments by index.

The {1} refers to the second positional argument, which is 'Bob'. The keyword argument 'score' is 95.

❓ Predict Output

intermediate

Using format() with alignment and width

What will this code print?

Python

print("|{:<10}|{:^10}|{:>10}|".format('left', 'center', 'right'))

A |left |center | right|

B | left| center |right |

C |left|center|right|

D |left | center | right|

💡 Hint

Check the alignment symbols: < for left, ^ for center, > for right.

The first field is left aligned in 10 spaces, second centered, third right aligned.

🧠 Conceptual

advanced

Understanding nested replacement fields

What is the output of this code?

Python

data = {'name': 'John', 'age': 30}
print("{0[name]} is {0[age]} years old".format(data))

A John is 30 years old

B {0[name]} is {0[age]} years old

C TypeError

D KeyError

💡 Hint

The 0 refers to the first argument, which is a dictionary.

The format method accesses dictionary keys inside the replacement fields.

❓ Predict Output

advanced

Formatting floats with precision and padding

What does this code print?

Python

print("{num:0>8.3f}".format(num=12.34567))

A 12.34600

B 0012.346

C 000012.3467

D 12.34567

💡 Hint

0>8 means pad with zeros on the left to width 8, .3f means 3 decimal places.

The number is rounded to 3 decimals and padded with zeros on the left to fill 8 characters.

❓ Predict Output

expert

Using format() with dynamic field names and expressions

What is the output of this code?

Python

person = {'first': 'Jane', 'last': 'Doe'}
index = 'first'
print("{0[{1}]} {0[last]}".format(person, index))

A KeyError

B first Doe

C Jane Doe

D IndexError

💡 Hint

The second argument is used as a key to access the dictionary in the first argument.

The {0[{1}]} accesses person[index], which is person['first'] = 'Jane'.

Practice

1.

What does the format() method do in Python?

easy

A. It inserts values into a string at placeholders marked by {}.

B. It changes the case of a string to uppercase.

C. It splits a string into a list of words.

D. It removes whitespace from the start and end of a string.

Solution

1. Step 1: Understand the purpose of format()

   The format() method is used to insert values into a string where {} placeholders are present.

2. Step 2: Compare options

   Only It inserts values into a string at placeholders marked by {}. correctly describes this behavior. Other options describe different string methods.

3. Final Answer:

   It inserts values into a string at placeholders marked by {} -> Option A

4. Quick Check:

   format() inserts values into {} [OK]

Hint: Remember: {} marks where values go in format() [OK]

Common Mistakes:

• Confusing format() with upper() or strip()
• Thinking format() splits strings
• Assuming format() changes string case

2.

Which of the following is the correct syntax to insert the value 42 into the string using format()?

"The answer is {}"._____

easy

A. "format[42]"

B. "format 42"

C. "format{42}"

D. "format(42)"

Solution

1. Step 1: Recall correct method call syntax

   The format() method is called with parentheses and the value inside, like format(42).

2. Step 2: Check options for correct syntax

   Only "format(42)" uses parentheses correctly. Options A, C, and D use incorrect brackets or missing parentheses.

3. Final Answer:

   "format(42)" -> Option D

4. Quick Check:

   Method calls use parentheses () [OK]

Hint: Use parentheses () to call methods like format() [OK]

Common Mistakes:

• Using square brackets [] instead of parentheses
• Using curly braces {} instead of parentheses
• Omitting parentheses when calling methods

3.

What is the output of the following code?

print("{0} + {1} = {2}".format(3, 4, 3+4))

medium

A. "7 + 7 = 14"

B. "3 + 4 = 7"

C. "3 + 4 = 3+4"

D. "{0} + {1} = {2}"

Solution

1. Step 1: Understand placeholders and arguments

   The placeholders {0}, {1}, {2} are replaced by the first, second, and third arguments of format(), which are 3, 4, and 7 respectively.

2. Step 2: Substitute values into the string

   Replacing placeholders gives the string "3 + 4 = 7".

3. Final Answer:

   "3 + 4 = 7" -> Option B

4. Quick Check:

   Placeholders replaced by arguments [OK]

Hint: Numbered placeholders match format() arguments by position [OK]

Common Mistakes:

• Printing placeholders literally without replacement
• Confusing expression with string output
• Mixing up argument order

4.

Find the error in this code snippet:

"Hello, {}".format

medium

A. format() cannot be used with strings.

B. Incorrect placeholder syntax; should be {0}.

C. Missing parentheses to call the format method.

D. The string should use single quotes instead of double quotes.

Solution

1. Step 1: Check method call syntax

   The code uses format without parentheses, so the method is not called.

2. Step 2: Identify the fix

   Adding parentheses like format() calls the method and inserts values.

3. Final Answer:

   Missing parentheses to call the format method. -> Option C

4. Quick Check:

   Methods need () to execute [OK]

Hint: Always add () to call methods like format() [OK]

Common Mistakes:

• Forgetting parentheses when calling methods
• Thinking placeholders must be numbered
• Believing quotes style affects format()

5.

How would you format the number 7.12345 to show only two decimal places using format()?

"{:.2f}".format(7.12345)

What is the output?

hard

A. "7.12"

B. "7.12345"

C. "7.1"

D. "7.00"

Solution

1. Step 1: Understand format specifier :.2f

   This means format the number as a float with 2 digits after the decimal point.

2. Step 2: Apply formatting to 7.12345

   The number rounds to 7.12 when limited to two decimal places.

3. Final Answer:

   "7.12" -> Option A

4. Quick Check:

   Two decimals with :.2f rounds number [OK]

Hint: Use {:.2f} to format floats with 2 decimals [OK]

Common Mistakes:

• Not using format specifiers correctly
• Expecting original number without rounding
• Confusing decimal places with total digits