Automatic resource cleanup in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a file using a context manager.

Python

with open('example.txt', [1]) as file:
    content = file.read()

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

A'open'

B'r'

C'write'

D'close'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write' instead of 'r' causes the file to open for writing, which may overwrite content.

Using 'open' or 'close' as mode strings are invalid.

The mode 'r' opens the file for reading, which is the default and correct here.

2fill in blank

medium

Complete the code to automatically close the file after reading.

Python

with open('data.txt', 'r') as [1]:
    data = file.read()

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

Afile

Bread

Copen

Df

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'open' or 'read' as variable names causes errors.

Using 'f' is common but here 'file' matches the code below.

The variable name after 'as' is used to refer to the file object inside the block.

3fill in blank

hard

Fix the error in the code to ensure the file is closed automatically.

Python

file = open('log.txt', 'r')
try:
    content = [1].read()
finally:
    file.close()

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

Afile

Bopen

Cread

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'open.read()' causes an error because open is a function, not the file object.

Using 'read.read()' or 'close.read()' are invalid.

The variable 'file' holds the file object and must be used to call read().

4fill in blank

hard

Fill both blanks to create a dictionary with word lengths for words longer than 3 characters.

Python

lengths = {word: [1] for word in words if len(word) [2] 3}

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

Alen(word)

B>

C<

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' filters shorter words.

Using 'word' instead of len(word) gives the word itself, not its length.

We use len(word) to get the length and '>' to filter words longer than 3 characters.

5fill in blank

hard

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

Python

result = [1]: [2] for k, v in data.items() if v [3] 0}

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

Ak.upper()

Bv

C>

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'k' instead of 'k.upper()' keeps keys as original case.

Using '<' instead of '>' filters values less than zero.

Using 'k' or 'v' incorrectly in keys or values.

Keys are converted to uppercase with k.upper(), values are v, and we filter values greater than zero using '>'.

Practice

1. What is the main purpose of using the with statement in Python for resource management?

easy

A. To create infinite loops easily

B. To automatically release resources like files or locks after use

C. To define functions inside other functions

D. To import modules dynamically

Solution

1. Step 1: Understand resource management

   The with statement is designed to handle resources such as files or locks safely.

2. Step 2: Identify automatic cleanup

   It ensures resources are released automatically after the block finishes, preventing leaks.

3. Final Answer:

   To automatically release resources like files or locks after use -> Option B

4. Quick Check:

   Automatic cleanup = To automatically release resources like files or locks after use [OK]

Hint: Think: with = automatic resource release [OK]

Common Mistakes:

• Confusing with loops or function definitions
• Thinking it imports modules
• Assuming manual cleanup is still needed

2. Which of the following is the correct syntax to open a file for reading using automatic resource cleanup?

easy

A. open with('file.txt', 'r') as f:

B. with open('file.txt', 'r') f:

C. with open('file.txt', 'r') as f:

D. open('file.txt', 'r') with as f:

Solution

1. Step 1: Recall correct with syntax

   The correct syntax starts with with, followed by the resource expression, then as and a variable.

2. Step 2: Match syntax to options

   with open('file.txt', 'r') as f: matches the correct pattern: with open('file.txt', 'r') as f:

3. Final Answer:

   with open('file.txt', 'r') as f: -> Option C

4. Quick Check:

   Correct with syntax = with open('file.txt', 'r') as f: [OK]

Hint: Remember: with + resource + as + variable [OK]

Common Mistakes:

• Misplacing 'with' keyword
• Omitting 'as' keyword
• Wrong order of keywords

3. What will be the output of this code?

with open('test.txt', 'w') as f:
    f.write('Hello')
print(f.closed)

medium

A. Error: f is not defined

B. False

C. Hello

D. True

Solution

1. Step 1: Understand the with block effect

   The file is opened and written inside the with block, which automatically closes the file after the block ends.

2. Step 2: Check the f.closed property after block

   After the block, the variable f is out of scope and not defined, so accessing f.closed raises a NameError.

3. Final Answer:

   Error: f is not defined -> Option A

4. Quick Check:

   Variable f is local to with block, so f.closed access outside causes error [OK]

Hint: f is only defined inside with block; outside it is undefined [OK]

Common Mistakes:

• Thinking file stays open after with block
• Expecting file content as output
• Assuming f is defined outside with

4. Identify the error in this code snippet:

with open('data.txt', 'r') as file:
    content = file.read()
file.close()

medium

A. No error, code is correct

B. Missing colon after with statement

C. Indentation error on content assignment

D. Calling file.close() is unnecessary and causes an error

Solution

1. Step 1: Understand automatic closing with with

   The with statement automatically closes the file after the block ends.

2. Step 2: Check explicit close call

   Calling file.close() outside the block is unnecessary, but Python file objects handle multiple calls to close() gracefully without raising an error.

3. Final Answer:

   No error, code is correct -> Option A

4. Quick Check:

   Explicit close after with = no error [OK]

Hint: with handles closing; extra close() is harmless [OK]

Common Mistakes:

• Believing file.close() causes an error after with
• Looking for syntax errors like missing colon
• Suspecting indentation problems

5. You want to safely acquire and release a lock using automatic resource cleanup. Which code snippet correctly uses with for this purpose?

import threading
lock = threading.Lock()

# Choose the correct usage
A) with lock.acquire():
       print('Lock acquired')
B) with lock.acquire:
       print('Lock acquired')
C) with lock:
       print('Lock acquired')
D) with lock.lock():
       print('Lock acquired')

hard

A. with lock.acquire():

B. with lock.acquire:

C. with lock.lock():

D. with lock:

Solution

1. Step 1: Understand lock context management

   Python's threading.Lock supports the context manager protocol, so you can use with lock: to acquire and release automatically.

2. Step 2: Analyze options

   with lock: uses with lock:, which is correct. Other options misuse the acquire method or call non-existent methods.

3. Final Answer:

   with lock: -> Option D

4. Quick Check:

   Use lock directly in with = with lock: [OK]

Hint: Use 'with lock:' to auto acquire and release locks [OK]

Common Mistakes:

• Calling lock.acquire() inside with
• Using wrong method names
• Not knowing Lock supports context manager