advancedAdvanced Topics

Context Managers

Manage resources safely with the with statement.

In this lesson

01The With Statement
02contextlib

01The With Statement

Context managers handle setup and teardown of resources automatically.

Python

1# File context manager (built-in)
2with open("test.txt", "w") as f:
3    f.write("Hello!")
4# File is automatically closed here
5
6# Custom context manager with class
7class DatabaseConnection:
8    def __enter__(self):
9        print("Connecting to DB...")
10        return self
11    
12    def __exit__(self, exc_type, exc_val, exc_tb):
13        print("Closing connection.")
14        return False
15
16with DatabaseConnection() as db:
17    print("Running queries...")

Output

Connecting to DB...
Running queries...
Closing connection.

02contextlib

Use contextlib for simpler context manager creation.

Python

1from contextlib import contextmanager
2
3@contextmanager
4def tag(name):
5    print(f"<{name}>")
6    yield
7    print(f"</{name}>")
8
9with tag("div"):
10    print("  Hello, World!")

Output

<div>
  Hello, World!
</div>

Generators & Iterators

Regular Expressions