Iteration using range() in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 0 to 4 using a for loop and range().

Python

for i in [1](5):
    print(i)

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

Arange

Blist

Ctuple

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using list(5) instead of range(5) causes an error.

Using tuple(5) or set(5) is invalid for iteration.

The range(5) function generates numbers from 0 up to 4. Using it in the for loop lets us print these numbers one by one.

2fill in blank

medium

Complete the code to print numbers from 3 to 7 using range().

Python

for num in [1](3, 8):
    print(num)

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Atuple

Blist

Crange

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using 7 as the stop value will exclude 7 from the output.

Using list or tuple instead of range causes errors.

range(3, 8) generates numbers starting at 3 up to 7 (8 is excluded). This lets the loop print numbers 3 to 7.

3fill in blank

hard

Fix the error in the code to print even numbers from 2 to 10 using range().

Python

for x in range(2, 11, [1]):
    print(x)

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A2

B1

C3

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using step 1 prints all numbers, not just even ones.

Using step 3 or 4 skips some even numbers.

The third argument in range is the step. Using 2 steps moves from 2 to 4, 6, 8, 10, printing even numbers.

4fill in blank

hard

Fill both blanks to create a dictionary with numbers from 1 to 5 as keys and their squares as values.

Python

squares = {x: x[1]2 for x in [2](1, 6)}

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A**

B*

Crange

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using * instead of ** calculates double the number, not square.

Using list instead of range causes errors in dictionary comprehension.

Using range(1, 6) generates numbers 1 to 5. The expression x**2 calculates the square of each number. Together, they create the dictionary of squares.

5fill in blank

hard

Fill all three blanks to create a dictionary with uppercase letters as keys and their positions as values for letters A to E.

Python

letters = [1]: [2] for [3] in range(1, 6)}

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Achr(i + 64)

Bi

Dchr(i)

Attempts:

3 left

💡 Hint

Common Mistakes

Using chr(i) gives wrong letters because ASCII codes start at 65 for 'A'.

Using wrong loop variable name causes errors.

The chr(i + 64) converts numbers 1 to 5 into letters A to E. The key is the letter, and the value is the number i. The loop variable is i.

Practice

1. What does range(5) do in a Python for loop?

easy

A. Generates numbers from 0 to 4

B. Generates numbers from 1 to 5

C. Generates numbers from 0 to 5

D. Generates numbers from 1 to 4

Solution

1. Step 1: Understand the range function

   range(5) starts at 0 by default and stops before 5.

2. Step 2: Identify the numbers generated

   The numbers generated are 0, 1, 2, 3, 4.

3. Final Answer:

   Generates numbers from 0 to 4 -> Option A

4. Quick Check:

   range(5) = 0,1,2,3,4 [OK]

Hint: Remember range stops before the end number [OK]

Common Mistakes:

• Thinking range(5) includes 5
• Starting count at 1 by default
• Confusing stop value as inclusive

2. Which of the following is the correct syntax to loop 3 times using range()?

easy

A. for i in range(1, 3):

B. for i in range(3):

C. for i in range(0, 3, 2):

D. for i in range(3, 0):

Solution

1. Step 1: Check each range syntax

   for i in range(1, 3): loops from 1 to 2 (2 times), for i in range(3): loops 0 to 2 (3 times), for i in range(0, 3, 2): loops 0 and 2 (2 times), for i in range(3, 0): runs zero times because start > stop without negative step.

2. Step 2: Identify the correct loop count

   Only for i in range(3): loops exactly 3 times: 0,1,2.

3. Final Answer:

   for i in range(3): -> Option B

4. Quick Check:

   range(3) loops 3 times [OK]

Hint: range(n) loops exactly n times starting at 0 [OK]

Common Mistakes:

• Using range(1, 3) which loops 2 times
• Using invalid range with start > stop
• Confusing step parameter

3. What is the output of this code?

for i in range(2, 7, 2):
    print(i, end=' ')

medium

A. 0 2 4 6

B. 2 3 4 5 6

C. 2 4 6 8

D. 2 4 6

Solution

1. Step 1: Understand the range parameters

   range(2, 7, 2) starts at 2, stops before 7, stepping by 2.

2. Step 2: List the numbers generated

   Numbers are 2, 4, 6.

3. Final Answer:

   2 4 6 -> Option D

4. Quick Check:

   range(2,7,2) = 2,4,6 [OK]

Hint: Start, stop, step control numbers generated [OK]

Common Mistakes:

• Including 7 in output
• Using wrong step size
• Starting from 0 instead of 2

4. Find the error in this code:

for i in range(5, 1):
    print(i)

medium

A. No error, prints 5 to 1

B. SyntaxError due to wrong range syntax

C. Loop does not run because start > stop without step

D. Infinite loop

Solution

1. Step 1: Analyze the range parameters

   range(5, 1) means start at 5, stop before 1, with default step 1.

2. Step 2: Understand loop behavior

   Since start is greater than stop and step is positive, the loop runs zero times.

3. Final Answer:

   Loop does not run because start > stop without step -> Option C

4. Quick Check:

   range(5,1) empty range [OK]

Hint: Positive step needs start < stop to run [OK]

Common Mistakes:

• Expecting loop to run backwards
• Thinking syntax error occurs
• Assuming infinite loop

5. You want to print all odd numbers from 1 to 15 using range(). Which code does this correctly?

hard

A. for i in range(1, 16, 2): print(i)

B. for i in range(0, 15, 2): print(i)

C. for i in range(1, 15): if i % 2 == 1: print(i)

D. for i in range(1, 16): print(i % 2)

Solution

1. Step 1: Identify odd numbers range

   Odd numbers from 1 to 15 are 1,3,5,...,15.

2. Step 2: Check each option

   for i in range(1, 16, 2): print(i) uses range(1,16,2) which generates 1,3,5,...,15 directly. for i in range(0, 15, 2): print(i) starts at 0 (even). for i in range(1, 15): if i % 2 == 1: print(i) misses 15 (range(1,15) goes to 14) and uses extra if check. for i in range(1, 16): print(i % 2) prints 1 or 0, not numbers.

3. Final Answer:

   for i in range(1, 16, 2): print(i) -> Option A

4. Quick Check:

   range(1,16,2) = odd numbers [OK]

Hint: Use step=2 starting at 1 for odd numbers [OK]

Common Mistakes:

• Starting at 0 for odd numbers
• Forgetting to include last number
• Printing modulo instead of number