A method is a function associated with an object or class and invoked through that association. It packages behavior with the data it operates on. section 10.1
Define methods inside a class. Python passes the invoked instance as the first argument, conventionally named self, so the method can read or change attributes such as self.flavor. The name self is a convention rather than a reserved word, but tools and Python programmers expect it. section 10.6
Move an operation onto its data
A standalone average(numbers) function leaves callers responsible for supplying and understanding a list. A ScoreList class can store the scores and expose average() directly: scores = ScoreList([...]); scores.average(). The calculation stays the same, while the interface expresses the domain more clearly. section 10.1
When implementing or using methods, remember:
- Put the instance parameter first and normally call it self; include additional parameters for the operation's inputs. section 10.6
- Use methods to express relationships between objects, such as Shelf.add_book, Shelf.has_book, and Shelf.total_price. section 10.12
- Practice methods alongside attributes, composition, inheritance, and class-level behavior when building Python objects. section 10.3
class ScoreList():
def __init__(self, scores):
self.scores = scores
def average(self):
return sum(self.scores) / len(self.scores)
scores = ScoreList([85, 95, 98, 87, 80, 92])
print(f'The final score is {scores.average()}.')
Compare a regular function with a method attached to ScoreList and invoked through an instance. section 10.1
