sum() function in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the sum of numbers in the list.

Python

numbers = [1, 2, 3, 4, 5]
total = [1](numbers)
print(total)

Drag options to blanks, or click blank then click option'

Amin

Blen

Cmax

Dsum

Attempts:

3 left

💡 Hint

Common Mistakes

Using len() instead of sum() which returns the count, not the total.

Using max() or min() which return the largest or smallest number, not the sum.

The sum() function adds all numbers in the list and returns the total.

2fill in blank

medium

Complete the code to calculate the sum of numbers from 1 to 5 using range.

Python

total = [1](range(1, 6))
print(total)

Drag options to blanks, or click blank then click option'

Amax

Bsum

Clen

Dmin

Attempts:

3 left

💡 Hint

Common Mistakes

Using len() which returns the count of numbers, not their sum.

Using max() or min() which return single values, not the total.

The sum() function can add numbers generated by range().

3fill in blank

hard

Fix the error in the code to correctly sum the list elements.

Python

values = [10, 20, 30]
total = sum[1]values
print(total)

Drag options to blanks, or click blank then click option'

A{ }

B[ ]

C( )

D< >

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets which are for lists, not function calls.

Using curly braces or angle brackets which are invalid here.

The sum() function requires parentheses around its argument.

4fill in blank

hard

Fill both blanks to create a dictionary of word lengths for words longer than 3 letters.

Python

words = ['apple', 'bat', 'carrot', 'dog']
lengths = {word: [1] for word in words if len(word) [2] 3}
print(lengths)

Drag options to blanks, or click blank then click option'

Alen(word)

Bword

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using the word itself instead of its length.

Using the wrong comparison operator like <= which selects shorter words.

We use len(word) to get the length and filter words with length greater than 3 using >.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase keys and values greater than 10.

Python

data = {'a': 5, 'b': 15, 'c': 20}
result = { [1]: [2] for k, v in data.items() if v [3] 10 }
print(result)

Drag options to blanks, or click blank then click option'

Ak.upper()

Bv

C>

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using original keys without uppercase.

Using wrong comparison operators like < instead of >.

Using keys instead of values in the dictionary.

The keys are converted to uppercase with k.upper(), values are v, and filtered where v > 10.

Practice

1. What does the sum() function do in Python?

easy

A. Counts the number of elements in an iterable

B. Multiplies all numbers in an iterable

C. Adds all numbers in an iterable and returns the total

D. Finds the largest number in an iterable

Solution

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

   The sum() function takes an iterable like a list or tuple and adds all its numbers together.

2. Step 2: Compare options with the function's behavior

   Only Adds all numbers in an iterable and returns the total correctly describes adding all numbers and returning the total.

3. Final Answer:

   Adds all numbers in an iterable and returns the total -> Option C

4. Quick Check:

   sum() adds numbers [OK]

Hint: Remember: sum() adds, not multiplies or counts [OK]

Common Mistakes:

• Confusing sum() with multiplication
• Thinking sum() counts elements
• Assuming sum() finds max value

2. Which of the following is the correct syntax to sum numbers in a list nums starting from 10?

easy

A. sum(nums, 10)

B. sum(10, nums)

C. sum(nums + 10)

D. sum(start=10, nums)

Solution

1. Step 1: Recall the sum() function signature

   The sum() function syntax is sum(iterable, start=0), where the second argument is the starting value.

2. Step 2: Identify correct argument order

   sum(nums, 10) uses sum(nums, 10), which correctly passes the iterable first and start second.

3. Final Answer:

   sum(nums, 10) -> Option A

4. Quick Check:

   sum(iterable, start) = sum(nums, 10) [OK]

Hint: Iterable first, start second in sum() [OK]

Common Mistakes:

• Swapping the order of arguments
• Using plus sign inside sum()
• Using keyword argument incorrectly

3. What is the output of the following code?

numbers = [2, 4, 6]
result = sum(numbers, 5)
print(result)

medium

A. Error

B. 12

C. 11

D. 17

Solution

1. Step 1: Calculate sum of list elements

   The list numbers contains 2, 4, and 6. Their sum is 2 + 4 + 6 = 12.

2. Step 2: Add the start value

   The start value is 5, so total is 12 + 5 = 17.

3. Final Answer:

   17 -> Option D

4. Quick Check:

   sum([2,4,6],5) = 17 [OK]

Hint: Add start value after summing list [OK]

Common Mistakes:

• Forgetting to add the start value
• Adding start value before summing
• Assuming sum returns list length

4. The code below throws an error. What is the problem?

values = [1, 2, '3', 4]
total = sum(values)

medium

A. sum() requires a start argument

B. List contains a string which cannot be added

C. sum() only works with tuples

D. Missing parentheses in sum() call

Solution

1. Step 1: Check list element types

   The list values contains integers and a string '3'. sum() cannot add strings to numbers.

2. Step 2: Understand sum() type requirements

   sum() requires all elements to be numbers. Mixing types causes a TypeError.

3. Final Answer:

   List contains a string which cannot be added -> Option B

4. Quick Check:

   sum() needs all numbers [OK]

Hint: Ensure all list items are numbers before sum() [OK]

Common Mistakes:

• Ignoring mixed data types
• Thinking sum() needs start argument
• Assuming sum() works on strings

5. You have a list of daily sales: sales = [100, 200, 0, 150, 300]. You want to calculate the total sales but ignore days with zero sales. Which code correctly uses sum() to do this?

hard

A. sum(sale for sale in sales if sale != 0)

B. sum(sales) - sales.count(0)

C. sum(sales, 0) if 0 not in sales else 0

D. sum(sales) / sales.count(0)

Solution

1. Step 1: Filter out zero sales using a generator expression

   The expression sale for sale in sales if sale != 0 creates a sequence of sales excluding zeros.

2. Step 2: Use sum() on filtered sales

   sum() adds only the non-zero sales, giving the correct total.

3. Final Answer:

   sum(sale for sale in sales if sale != 0) -> Option A

4. Quick Check:

   sum(filtered sales) = correct total [OK]

Hint: Use sum() with condition inside generator [OK]

Common Mistakes:

• Subtracting the count of zeros instead of filtering
• Using sum() with wrong condition
• Dividing sum by zero count