Python Block Structure and Indentation - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

What will Python raise if the print line is not indented inside the function?

Python

def greet():
print("Hello")
# Python raises: [1]

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

AIndentationError

BSyntaxError

CNameError

DTypeError

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing IndentationError with SyntaxError — IndentationError is a subclass of SyntaxError but more specific.

Thinking missing indentation causes a runtime error instead of a parse-time error.

Python raises IndentationError when a statement that should be inside a block is not indented. The print must be indented under def.

2fill in blank

medium

How many spaces does Python's PEP 8 standard recommend per indentation level?

Python

# PEP 8 recommends [1] spaces per indent level
def example():
    if True:
        pass  # this line is 2 levels deep

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

A2

B4

C8

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 2 spaces — common in other languages but not Python's standard.

Mixing tabs and spaces which causes IndentationError.

Python's PEP 8 style guide recommends 4 spaces per indentation level. The pass line is 2 levels deep so it uses 8 spaces total (2 × 4).

3fill in blank

hard

What does this code print? Pay close attention to which print belongs inside the loop.

Python

for i in range(3):
    print("A")
print("B")
# Total lines printed: [1]

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

A3

B1

C6

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking both prints are inside the loop — only the indented one is.

Forgetting that the unindented print runs once after the loop.

The indented print("A") runs 3 times inside the loop. The unindented print("B") runs once after the loop ends. Total output: 4 lines (A, A, A, B).

4fill in blank

hard

Fill both blanks. The return statement's indentation decides when the function returns.

Python

def add_until(n):
    total = 0
    for i in range(1, n+1):
        total += i
    return total

print(add_until(3))
# Output: [1]
# return belongs to the [2] block

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

A6

B1

Cfunction

Dloop

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking return is inside the loop — check its indentation level.

Confusing function-level and loop-level indentation.

The return is at the function level (one indent), not inside the loop. So the loop completes fully (1+2+3=6) before returning. If return were indented inside the loop, it would return 1 on the first iteration.

5fill in blank

hard

Fill all three blanks. Determine each output line based on which block each print belongs to.

Python

x = 10
if x > 5:
    print("big")
    if x > 8:
        print("very big")
print("done")
# Line 1: [1]
# Line 2: [2]
# Line 3: [3]

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

Abig

Bvery big

Cdone

Dnothing

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking 'done' only prints when conditions are true — it is outside all if blocks.

Missing the nested if block — the second indent level creates a block inside a block.

Since x=10: the outer if x > 5 is true → prints big. The nested if x > 8 is also true → prints very big. The unindented print("done") always runs because it is outside all if blocks.

Practice

1. What does indentation in Python indicate?

easy

A. Which lines of code belong together in a block

B. The data type of a variable

C. The speed of code execution

D. The name of a function

Solution

1. Step 1: Understand Python's use of indentation

   Python uses indentation to group lines of code that belong to the same block, like inside a function or loop.

2. Step 2: Identify what indentation shows

   Indentation shows which lines are connected logically and executed together.

3. Final Answer:

   Which lines of code belong together in a block -> Option A

4. Quick Check:

   Indentation = Code blocks [OK]

Hint: Indentation groups code lines into blocks [OK]

Common Mistakes:

• Thinking indentation shows variable types
• Confusing indentation with execution speed
• Assuming indentation names functions

2. Which of the following code snippets has correct indentation in Python?

easy

A. def greet():
print('Hello')
print('World')

B. def greet():
print('Hello')
print('World')

C. def greet():
print('Hello')
print('World')

D. def greet():
print('Hello')
print('World')

Solution

1. Step 1: Check indentation inside the function

   All lines inside the function must be indented the same amount to belong to the function block.

2. Step 2: Identify the snippet with consistent indentation

   def greet():
     print('Hello')
     print('World')

   has both print statements indented equally under the function, which is correct.

3. Final Answer:

   def greet():\n print('Hello')\n print('World') -> Option D

4. Quick Check:

   Consistent indentation inside function = Correct [OK]

Hint: Indent all block lines equally under the header [OK]

Common Mistakes:

• Mixing indentation levels inside a block
• Not indenting any lines inside a function
• Indenting only some lines inconsistently

3. What will be the output of this code?

for i in range(2):
    print('Start')
    if i == 0:
        print('First loop')
    print('End')

medium

A. Start\nFirst loop\nEnd\nStart\nEnd

B. Start\nEnd\nStart\nFirst loop\nEnd

C. Start\nFirst loop\nEnd\nStart\nFirst loop\nEnd

D. Start\nEnd\nStart\nEnd

Solution

1. Step 1: Trace the loop iterations

   The loop runs twice: i=0 and i=1.

2. Step 2: Check prints for each iteration

   For i=0: prints 'Start', then 'First loop' (because i==0), then 'End'. For i=1: prints 'Start' and 'End' only.

3. Final Answer:

   Start\nFirst loop\nEnd\nStart\nEnd -> Option A

4. Quick Check:

   Loop with condition prints extra line only once [OK]

Hint: Follow indentation to see which prints run inside conditions [OK]

Common Mistakes:

• Ignoring indentation and printing 'First loop' twice
• Mixing order of printed lines
• Assuming all prints run every iteration

4. Identify the error in this code:

if True:
print('Yes')
    print('Still Yes')

medium

A. SyntaxError because of missing colon

B. IndentationError due to inconsistent indentation

C. No error, code runs fine

D. NameError due to undefined variable

Solution

1. Step 1: Check indentation after if statement

   Lines inside the if block must be indented equally.

2. Step 2: Identify inconsistent indentation

   The first print is not indented, the second print is indented. This causes an IndentationError.

3. Final Answer:

   IndentationError due to inconsistent indentation -> Option B

4. Quick Check:

   Inconsistent indentation = IndentationError [OK]

Hint: All lines in a block must have same indentation [OK]

Common Mistakes:

• Thinking missing colon causes error here
• Assuming code runs without indentation
• Confusing IndentationError with NameError

5. You want to write a function that prints numbers 1 to 3, each followed by 'Done' on a new line. Which code correctly uses indentation to achieve this?

def print_numbers():
    for i in range(1, 4):
        print(i)
    print('Done')

hard

A. def print_numbers():
for i in range(1, 4):
print(i)
print('Done')

B. def print_numbers():
for i in range(1, 4):
print(i)
print('Done')

C. def print_numbers():
for i in range(1, 4):
print(i)
print('Done')

D. def print_numbers():
for i in range(1, 4):
print(i)
print('Done')

Solution

1. Step 1: Understand desired output

   Each number 1 to 3 should print, then 'Done' on a new line after each number.

2. Step 2: Check indentation for print statements

   To print 'Done' after each number, both print(i) and print('Done') must be inside the for loop, indented equally.

3. Step 3: Identify correct option

   def print_numbers():
       for i in range(1, 4):
           print(i)
           print('Done')

   has both prints indented inside the loop, so 'Done' prints after each number.

4. Final Answer:

   def print_numbers():\n for i in range(1, 4):\n print(i)\n print('Done') -> Option C

5. Quick Check:

   Same indentation inside loop = prints per iteration [OK]

Hint: Indent all loop actions equally to repeat each time [OK]

Common Mistakes:

• Indenting 'Done' outside loop causing single print
• Not indenting loop body at all
• Mixing indentation levels inside loop