__format__ — Easy Examples

Called by format() and f-strings for custom formatting

EasyIntermediateAdvancedExpert

Implementing __format__

Basic implementation of __format__ in a class.

python
class Example:
    def __format__(self):
        return "Example __format__"

obj = Example()
print(obj)

__format__ called by format() and f-strings for custom formatting. Implementing it lets you customize how Python interacts with your objects.

__format__ in action

Seeing __format__ called by Python's built-in operations.

python
# How Python calls __format__ automatically
class Demo:
    def __init__(self, value):
        self.value = value

    def __format__(self):
        print(f"__format__ was called!")
        return self

d = Demo(42)
# This triggers __format__:
print(d)

Python automatically calls __format__ when you use the corresponding operator or function on your object.

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