Let Custom Objects Use the 'with' Statement

The with open statement is a particularly convenient feature in Python, allowing for automatic closure of objects when operations are completed. For custom objects, it’s also possible to support the with syntax.

To achieve this, define the __enter__ and __exit__ methods in your class:

1
2
3
4
5
6
7

class MyClass(object):
    def __init__(self):
        pass
    def __enter__(self):
        print("Start")
    def __exit__(self, exc_type, exc_val, exc_tb):
        print("End")

With this setup, when using the with statement, it will first execute the content within __enter__, and automatically execute the content within __exit__ at the end of the code block.

1
2
3
4
5
6

>>> with MyClass() as tClass:
...     print("test")
...
Start
test
End