Best practices for resource management in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of using context manager with file handling

What is the output of this Python code snippet?

Python

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

A True

B False

C Raises a NameError

D None

💡 Hint

Think about what happens to the file after the with block ends.

The 'with' statement automatically closes the file after the block ends, so f.closed is True.

🧠 Conceptual

intermediate

Why use 'with' statement for resource management?

Which of the following best explains why using the 'with' statement is recommended for resource management in Python?

A It automatically handles opening and closing resources, even if errors occur.

B It makes the code run faster by caching resources.

C It allows resources to stay open indefinitely for reuse.

D It disables error messages related to resource usage.

💡 Hint

Think about what happens if an error occurs inside a 'with' block.

The 'with' statement ensures resources are properly closed even if exceptions happen, preventing leaks.

🔧 Debug

advanced

Identify the resource leak in this code

What is the main problem with this code snippet regarding resource management?

Python

def read_file(filename):
    f = open(filename, 'r')
    data = f.read()
    return data

content = read_file('data.txt')

A The file is opened in write mode instead of read mode.

B The file is closed too early before reading.

C The file is never closed, causing a resource leak.

D The function returns None instead of file content.

💡 Hint

Think about what happens to the file after reading.

The file is opened but never closed, which can exhaust system resources if done repeatedly.

📝 Syntax

advanced

Correct syntax for custom context manager

Which option correctly defines a custom context manager class in Python?

Python

class MyResource:
    def __enter__(self):
        print('Resource acquired')
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        print('Resource released')

A

class MyResource:
    def enter(self):
        return self
    def exit(self, exc_type, exc_val, exc_tb):
        pass

B

class MyResource:
    def __enter__(self):
        return self
    def __exit__(self, exc_type, exc_val, exc_tb):
        pass

C

class MyResource:
    def __enter__(self):
        return self
    def __exit__(self):
        pass

D

class MyResource:
    def __enter__(self):
        return self
    def __exit__(self, exc_type, exc_val):
        pass

💡 Hint

Check the method names and parameters required for context managers.

The __enter__ and __exit__ methods must have exact names and __exit__ must accept 4 parameters.

🚀 Application

expert

Using contextlib to manage resources

Which option correctly uses the contextlib module to create a context manager that prints messages on enter and exit?

Python

from contextlib import contextmanager

@contextmanager
def managed_resource():
    print('Start')
    yield
    print('End')

A

with managed_resource():
    print('Inside')

# Output:
# Start
# End
# Inside

B

with managed_resource:
    print('Inside')

# Output:
# Start
# Inside
# End

C

with managed_resource():
    print('Inside')

# Output:
# Inside
# Start
# End

D

with managed_resource():
    print('Inside')

# Output:
# Start
# Inside
# End

💡 Hint

Remember to call the function to get the context manager object.

The context manager must be called with parentheses; the yield separates enter and exit code.

Practice

1.

Why is it recommended to use the with statement when working with files in Python?

easy

A. It automatically closes the file after the block ends.

B. It makes the file open faster.

C. It prevents the file from being read.

D. It duplicates the file content.

Solution

1. Step 1: Understand the with statement role

   The with statement ensures that resources like files are properly closed after use, even if errors occur.

2. Step 2: Recognize automatic resource management

   Using with automatically calls the file's close() method when the block finishes.

3. Final Answer:

   It automatically closes the file after the block ends. -> Option A

4. Quick Check:

   with closes files automatically [OK]

Hint: Remember: with auto-closes resources [OK]

Common Mistakes:

• Thinking with speeds up file opening
• Believing with prevents reading
• Assuming with duplicates content

2.

Which of the following is the correct syntax to open a file named data.txt for reading using with?

?

easy

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

B. with open('data.txt') file:

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

D. with open('data.txt', 'read') as file:

Solution

1. Step 1: Recall correct open syntax

   The correct way to open a file for reading is open(filename, 'r').

2. Step 2: Check with statement syntax

   The with statement requires with open(...) as variable: format.

3. Final Answer:

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

4. Quick Check:

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

Hint: Use with open(filename, 'r') as var: [OK]

Common Mistakes:

• Omitting 'as' keyword
• Using 'read' instead of 'r' mode
• 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. True

B. False

C. Hello

D. Error

Solution

1. Step 1: Understand with block effect on file

   The with block opens the file and closes it automatically after the block ends.

2. Step 2: Check f.closed after block

   Since the file is closed after the block, f.closed will be True.

3. Final Answer:

   True -> Option A

4. Quick Check:

   File closed after with block = True [OK]

Hint: File is closed after with block ends [OK]

Common Mistakes:

• Thinking file stays open after with
• Expecting file content printed
• Confusing f.closed value

4.

Find the error in this code snippet:

file = open('log.txt', 'w')
file.write('Start logging')
# forgot to close the file

medium

A. File is not opened in read mode.

B. File name should be a variable.

C. File write syntax is incorrect.

D. File is not closed after writing.

Solution

1. Step 1: Check file opening and writing

   The file is opened correctly in write mode and data is written properly.

2. Step 2: Identify missing resource management

   The file is not closed after writing, which can cause data loss or resource leaks.

3. Final Answer:

   File is not closed after writing. -> Option D

4. Quick Check:

   Always close files after use [OK]

Hint: Always close files or use with [OK]

Common Mistakes:

• Ignoring missing close() call
• Thinking write syntax is wrong
• Confusing file modes

5.

You want to read multiple files and combine their contents safely. Which approach is best?

?

hard

A. Open all files without with and close manually later.

B. Use nested with statements to open each file safely.

C. Open files with open() but never close them.

D. Read files using open() without closing or with.

Solution

1. Step 1: Consider resource safety when reading multiple files

   Opening multiple files requires careful closing to avoid leaks or errors.

2. Step 2: Use nested with statements

   Nested with ensures each file is opened and closed properly, even if errors occur.

3. Final Answer:

   Use nested with statements to open each file safely. -> Option B

4. Quick Check:

   Nested with = safe multi-file handling [OK]

Hint: Use nested with for multiple files [OK]

Common Mistakes:

• Not closing files manually
• Opening many files without with
• Ignoring errors during file operations