Builder Pattern in Python
Builder is useful when an object has many optional parts or several valid configurations.
What is Builder Pattern?
Builder is useful when an object has many optional parts or several valid configurations.
Construct a complex object through clear, incremental steps.
When should you use it?
- Solve recurring object-design problems with proven structures.
- Decouple responsibilities so code is easier to extend and test.
- Use shared design vocabulary when discussing architecture with a team.
Example code
main.py
class ReportBuilder:
# Builder: assemble a complex value one optional part at a time.
def __init__(self):
self.parts = []
def add_title(self):
self.parts.append("title")
return self
def add_chart(self):
self.parts.append("chart")
return self
def build(self):
# Hide the final assembly behind one operation.
return "Report: " + ", ".join(self.parts)
report = ReportBuilder().add_title().add_chart().build()
print(report)Expected output
Report: title, chartHow it works
Chainable methods assemble the report while build returns the finished representation.
Change the values and run the program in the CodeUtility online Python compiler without installing Python locally.
Practice exercises
Modify the runnable example with the exercises below to build understanding beyond copying the result.
- Replace the sample domain while preserving the pattern structure.
- Compare the pattern with a simpler implementation and explain the tradeoff.
- Write tests for each participant before adding another implementation.