Builder
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The big picture
The Builder pattern helps you create an object made of several parts, in multiple steps, while keeping the code easy to read.
Instead of calling a constructor with 12 arguments—half of them None—you chain explicit methods (with_dough(), with_sauce(), etc.) and finish with build().
Key idea: separate how you build the object from what you get at the end. The builder
collects choices; build() returns the final product.
It shines when:
- many options are optional;
- the order of steps matters;
- you want to avoid half-built objects (until
build()runs).
Example: building a pizza step by step
Imagine a Pizza assembled incrementally. The builder makes each choice visible in code.
Chargement…
Sortie console
Pizza(dough:thin, sauce:tomato, topping:mozzarella, topping:basil)
Each builder method returns self, which powers the .dough(...).sauce(...).build() chain.
Example: configuring a data report
Same idea in data work: a report may have a title, filters, sort order, and export format—without cramming everything into one constructor.
Chargement…
Sortie console
Q1 Sales | filters=[('region', '=', 'EU'), ('amount', '>', 1000)] | sort=date | export=xlsx
Here the builder avoids a call like Report(title, filters, sort, format, ...) that is hard to read and painful to extend when you add another option.