Formatting using format() method in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the format() method do in Python?

It inserts values into a string at placeholders marked by curly braces {}, allowing you to create formatted strings easily.

beginner

How do you insert multiple values using format()?

Use multiple curly braces {} in the string and pass the values in order to format(). For example: '{} {}'.format('Hello', 'World') results in 'Hello World'.

intermediate

How can you specify the order of values in format()?

Use numbers inside the curly braces to indicate the position of the argument. For example: '{1} {0}'.format('first', 'second') results in 'second first'.

intermediate

How do you format a number to show 2 decimal places using format()?

Use a format specifier inside the braces like {:.2f}. For example: '{:.2f}'.format(3.14159) results in '3.14'.

intermediate

What happens if you use named placeholders in format()?

You can name placeholders like {name} and pass values as keyword arguments. For example: 'Hello {name}'.format(name='Alice') results in 'Hello Alice'.

What will '{} {}'.format('Good', 'Morning') output?

A 'Good Morning'

B '{} {}'

C 'Morning Good'

D 'Good{}Morning'

The format() method replaces the curly braces with the values in order, so it outputs 'Good Morning'.

How do you format the number 7.12345 to show only 3 decimal places?

A '{:.3}'.format(7.12345)

B '{3f}'.format(7.12345)

C '{:.3f}'.format(7.12345)

D '{3}'.format(7.12345)

The format specifier {:.3f} means 3 decimal places floating point.

What does '{1} {0}'.format('first', 'second') output?

A 'first second'

B 'second first'

C '{1} {0}'

D 'first first'

The numbers inside braces specify the argument index, so {1} is 'second' and {0} is 'first'.

Which is the correct way to use named placeholders?

A 'Hello {0}'.format(name='Bob')

B 'Hello {}'.format(name='Bob')

C 'Hello {name}'.format('Bob')

D 'Hello {name}'.format(name='Bob')

Named placeholders require matching keyword arguments in format().

What will 'Price: ${:.2f}'.format(4.5) output?

A 'Price: $4.50'

B 'Price: $4.5'

C 'Price: ${:.2f}'

D 'Price: $4'

The number is formatted to 2 decimal places, so 4.5 becomes 4.50.

Explain how to use the format() method to insert multiple values into a string.

Think about how you write placeholders and how you pass values to fill them.

Describe how to format a floating-point number to show exactly two decimal places using format().

Look for the part inside the curly braces that controls decimal places.

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