16.12. OOP Method Arguments
Methods are functions in the class
Prevents copy-paste code
Improves readability
Improves refactoring
Decomposes bigger problem into smaller chunks
At this moment:
At definition -
self
should always be a first parameterAt call -
self
is not passed as an argument (Python will do that)Later you will learn more advanced things like static methods etc.
- method
Functions in the class which takes instance as first argument (
self
)
16.12.1. Method Parameters
At definition -
self
should always be a first parameterLater you will learn more advanced things like static methods etc.
Parameter - Receiving variable used within the function
Parameters could be required or optional (with default value)
Required parameter:
Necessary to call that function
Specified at leftmost side
Optional parameter:
Has default value
Optional to call that function
Default value will be overridden if specified at a call time
Specified at rightmost side
Without parameters:
>>> class Astronaut:
... def say_hello(self):
... print('My name... José Jiménez')
Methods with required parameter:
>>> class Astronaut:
... def say_hello(self, firstname):
... print(f'My name... {firstname}')
Method with optional parameter:
>>> class Astronaut:
... def say_hello(self, firstname='unknown'):
... print(f'My name... {firstname}')
Method with required and optional parameter:
>>> class Astronaut:
... def say_hello(self, firstname, lastname='unknown'):
... print(f'My name... {firstname} {lastname}')
16.12.2. Method Arguments
At call -
self
is not passed as an argument (Python will do that)
>>> class Astronaut:
... def say_hello(self):
... print('My name... José Jiménez')
...
...
>>> jose = Astronaut()
>>> jose.say_hello()
My name... José Jiménez
Method with positional argument:
>>> class Astronaut:
... def say_hello(self, name):
... print(f'My name... {name}')
>>>
>>>
>>> jose = Astronaut()
>>>
>>> jose.say_hello('José Jiménez')
My name... José Jiménez
>>>
>>> jose.say_hello()
Traceback (most recent call last):
TypeError: Astronaut.say_hello() missing 1 required positional argument: 'name'
Method with keyword argument:
>>> class Astronaut:
... def say_hello(self, firstname, lastname):
... print(f'My name... {firstname} {lastname}')
>>>
>>>
>>> jose = Astronaut()
>>>
>>> jose.say_hello(firstname='José', lastname='Jiménez')
My name... José Jiménez
>>>
>>> jose.say_hello(lastname='Jiménez', firstname='José')
My name... José Jiménez
>>>
>>> jose.say_hello()
Traceback (most recent call last):
TypeError: Astronaut.say_hello() missing 2 required positional arguments: 'firstname' and 'lastname'
16.12.3. Assignments
"""
* Assignment: OOP Method Syntax
* Type: class assignment
* Complexity: easy
* Lines of code: 3 lines
* Time: 3 min
English:
1. Define class `Calculator`
2. Define method `add` in class `Calculator`
3. Method `add` take `a` and `b` as arguments
4. Method returns sum of `a` and `b`
5. Run doctests - all must succeed
Polish:
1. Zdefiniuj klasę `Calculator`
2. Zdefiniuj metodę `add` w klasie `Calculator`
3. Metoda `add` przyjmuje `a` i `b` jako argumenty
4. Metoda zwraca sumę `a` i `b`
5. Uruchom doctesty - wszystkie muszą się powieść
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> from inspect import isclass, ismethod
>>> assert isclass(Calculator)
>>> calc = Calculator()
>>> assert ismethod(calc.add)
>>> calc.add(1, 2)
3
"""
"""
* Assignment: OOP Method Mean
* Type: class assignment
* Complexity: easy
* Lines of code: 4 lines
* Time: 5 min
English:
1. Define class `Stats`
2. Define method `mean()` in `Stats` class
3. Method takes `data: list[float]` as an argument
4. Method returns arithmetic mean of the `data`
5. Returned value must be rounded to one decimal places
6. Run doctests - all must succeed
Polish:
1. Zdefiniuj klasę `Stats`
2. Zdefiniuj metodę `mean()` w klasie `Stats`
3. Metoda przyjmuje `data: list[float]` jako argument
4. Metoda zwraca średnią arytmetyczną z `data`
5. Zwracana wartość ma być zaokrąglona do jednego miejsca po przecinku
6. Uruchom doctesty - wszystkie muszą się powieść
Hints:
* `round()`
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> from inspect import isclass, ismethod
>>> assert isclass(Stats)
>>> stats = Stats()
>>> assert ismethod(stats.mean)
>>> stats.mean([1, 2])
1.5
>>> stats.mean([5.8, 2.7, 5.1, 1.9])
3.9
"""
"""
* Assignment: OOP Method Call
* Type: class assignment
* Complexity: easy
* Lines of code: 1 lines
* Time: 3 min
English:
1. Iterate over `DATA` skipping header and separating features from labels
2. Call `mean()` method of `Stats` class instance passing list of features
3. Define `result: list[float]` with list of means from each row
4. Run doctests - all must succeed
Polish:
1. Iteruj po `DATA` pomijając nagłówek i rodzielając cechy od etykiet
2. Wywołuj metodę `mean()` instancji klasy `Stats` przekazując listę cech
3. Zdefiniuj `result: list[float]` z listą średnich każdego z wierszy
4. Uruchom doctesty - wszystkie muszą się powieść
Hints:
* `round()`
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> assert type(result) is list
>>> assert all(type(x) is float for x in result)
>>> result
[3.9, 2.5, 3.5, 4.1, 3.9, 2.4]
"""
DATA = [
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species'),
(5.8, 2.7, 5.1, 1.9, 'virginica'),
(5.1, 3.5, 1.4, 0.2, 'setosa'),
(5.7, 2.8, 4.1, 1.3, 'versicolor'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor'),
(4.7, 3.2, 1.3, 0.2, 'setosa'),
]
class Stats:
def mean(self, data):
avg = sum(data) / len(data)
return round(avg, 1)
stats = Stats()
# Apply `mean()` to each feature
# type: list[float]
result = ...