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Context Managers

Context managers in Python provide a clean and efficient way to manage resources. They ensure that resources are properly acquired and released, even in the presence of exceptions. The most common way to use a context manager is with the with statement.

with open("my_file.txt", "r") as f:
    file_contents = f.read()
    # ... process file_contents ...

# File automatically closed here, even if exceptions occur.

The with statement implicitly calls the context manager’s __enter__ method (to acquire the resource) and __exit__ method (to release the resource).

Custom Context Managers //Need to create this note

The contextlib module provides tools for creating custom context managers:

• contextlib.contextmanager: A decorator that simplifies creating context managers.

from contextlib import contextmanager

@contextmanager
def my_context_manager(arg):
    print(f"Entering context with arg: {arg}")
    try:
        yield arg  # The code within the 'with' block runs here
    except Exception as e:
        print(f"Exception in context: {e}")
        # Handle the exception, perhaps log it
    finally:
        print("Exiting context")

with my_context_manager(10) as value:
    print(f"Value inside context: {value}")
    # raise Exception("Something went wrong")

This is equivalent to a class-based approach but much more concise.

Related Notes:

• Exception Handling
• File Handling