6.3. Staticmethod¶
6.3.1. Rationale¶
Should not be in a class: method which don't use
selfin its bodyShould be in class: if method takes
selfand use it (it requires instances to work)If a method don't use
selfbut uses class as a namespace use@staticmethoddecoratorUsing class as namespace
No need to create a class instance
Will not pass instance (
self) as a first method argument
>>> class MyClass:
...
... @staticmethod
... def mymethod():
... pass
>>>
>>>
>>> MyClass.mymethod()
6.3.2. Example¶
>>> class Astronaut:
... def __init__(self):
... self.name = 'José Jiménez'
...
... def say_hello(self):
... print(f'My name... {self.name}')
...
... @staticmethod
... def say_goodbye():
... print('Goodbye')
6.3.3. Instances¶
>>> class MyClass:
... def say_hello(self):
... print('Hello')
>>>
>>>
>>> my = MyClass()
>>> my.say_hello()
Hello
>>> class MyClass:
... @staticmethod
... def say_hello():
... print('Hello')
>>>
>>> MyClass.say_hello()
Hello
6.3.4. Namespace¶
Functions on a high level of a module lack namespace:
>>> def add(a, b):
... return a + b
>>>
>>> def sub(a, b):
... return a - b
>>>
>>>
>>> add(1, 2)
3
>>> sub(8, 4)
4
When add and sub are in Calculator class (namespace) they get instance (self) as a first argument. Instantiating Calculator is not needed, as of functions do not read or write to instance variables:
>>> class Calculator:
...
... def add(self, a, b):
... return a + b
...
... def sub(self, a, b):
... return a - b
>>>
>>>
>>> Calculator.add(10, 20)
Traceback (most recent call last):
TypeError: add() missing 1 required positional argument: 'b'
>>>
>>> Calculator.sub(8, 4)
Traceback (most recent call last):
TypeError: add() missing 1 required positional argument: 'b'
>>>
>>> calc = Calculator()
>>> calc.add(1, 2)
3
>>> calc.sub(8, 4)
4
Class Calculator is a namespace for functions. @staticmethod remove instance (self) argument to method:
>>> class Calculator:
...
... @staticmethod
... def add(a, b):
... return a + b
...
... @staticmethod
... def sub(a, b):
... return a - b
>>>
>>>
>>> Calculator.add(1, 2)
3
>>> Calculator.sub(8, 4)
4
6.3.5. Use Cases¶
Http Client:
>>> class http:
...
... @staticmethod
... def get(url):
... ...
...
... @staticmethod
... def post(url, data):
... ...
>>>
>>>
>>> http.get('https://python.astrotech.io')
>>> http.post('https://python.astrotech.io', data={'astronaut': 'Mark Watney'})
Astronaut Hello:
>>> def astronaut_say_hello():
... print('hello')
>>>
>>> def astronaut_say_goodbye():
... print('goodbye')
>>>
>>>
>>> class Astronaut:
... pass
>>>
>>>
>>> a = Astronaut()
>>> astronaut_say_hello()
hello
>>> astronaut_say_goodbye()
goodbye
>>> class Astronaut:
... def say_hello(self):
... print('hello')
...
... def say_goodbye(self):
... print('goodbye')
>>>
>>>
>>> a = Astronaut()
>>> a.say_hello()
hello
>>> a.say_goodbye()
goodbye
>>>
>>> Astronaut.say_hello()
Traceback (most recent call last):
TypeError: say_hello() missing 1 required positional argument: 'self'
>>>
>>> Astronaut.say_goodbye()
Traceback (most recent call last):
TypeError: say_goodbye() missing 1 required positional argument: 'self'
>>> class Astronaut:
...
... @staticmethod
... def say_hello():
... print('hello')
...
... @staticmethod
... def say_goodbye():
... print('goodbye')
>>>
>>>
>>> Astronaut.say_hello()
hello
>>> Astronaut.say_goodbye()
goodbye
>>>
>>> astro = Astronaut()
>>> astro.say_hello()
hello
>>> astro.say_goodbye()
goodbye
Helper HabitatOS Z-Wave sensor model:
from datetime import datetime, timezone
from decimal import Decimal, InvalidOperation
import logging
from django.db import models
from django.utils.translation import ugettext_lazy as _
from habitat._common.models import HabitatModel
from habitat._common.models import MissionDateTime
from habitat.time import MissionTime
log = logging.getLogger('habitat.sensor')
def clean_unit(unit: str) -> str:
try:
return {
'C': 'celsius',
'F': 'fahrenheit',
'dB': 'decibel',
'lux': 'lux',
'%': 'percent',
}[unit]
except KeyError:
return None
def clean_type(type: str) -> str:
return type.lower().replace(' ', '-')
def clean_value(value: str) -> Decimal:
try:
return Decimal(value)
except InvalidOperation:
return Decimal(0)
def clean_device(device: str) -> str:
return device
def clean_datetime(dt: str) -> datetime:
try:
return datetime.strptime(dt, '%Y-%m-%d %H:%M:%S.%f+00:00').replace(tzinfo=timezone.utc)
except ValueError:
return datetime.strptime(dt, '%Y-%m-%d %H:%M:%S.%f')
class ZWaveSensor(HabitatModel, MissionDateTime):
TYPE_BATTERY_LEVEL = 'battery-level'
TYPE_POWER_LEVEL = 'powerlevel'
TYPE_TEMPERATURE = 'temperature'
TYPE_LUMINANCE = 'luminance'
TYPE_RELATIVE_HUMIDITY = 'relative-humidity'
TYPE_ULTRAVIOLET = 'ultraviolet'
TYPE_BURGLAR = 'burglar'
TYPE_CHOICES = [
(TYPE_BATTERY_LEVEL, _('Battery Level')),
(TYPE_POWER_LEVEL, _('Power Level')),
(TYPE_TEMPERATURE, _('Temperature')),
(TYPE_LUMINANCE, _('Luminance')),
(TYPE_RELATIVE_HUMIDITY, _('Relative Humidity')),
(TYPE_ULTRAVIOLET, _('Ultraviolet')),
(TYPE_BURGLAR, _('Burglar'))]
UNIT_CELSIUS = 'celsius'
UNIT_KELVIN = 'kelvin'
UNIT_FAHRENHEIT = 'fahrenheit'
UNIT_DECIBEL = 'decibel'
UNIT_LUMINANCE = 'lux'
UNIT_PERCENT = 'percent'
UNIT_DIMENSIONLESS = None
UNIT_CHOICES = [
(UNIT_DIMENSIONLESS, _('n/a')),
(UNIT_PERCENT, _('%')),
(UNIT_LUMINANCE, _('Lux')),
(UNIT_DECIBEL, _('dB')),
(UNIT_CELSIUS, _('°C')),
(UNIT_KELVIN, _('K')),
(UNIT_FAHRENHEIT, _('°F'))]
DEVICE_ATRIUM = 'c1344062-2'
DEVICE_ANALYTIC_LAB = 'c1344062-3'
DEVICE_OPERATIONS = 'c1344062-4'
DEVICE_TOILET = 'c1344062-5'
DEVICE_DORMITORY = 'c1344062-6'
DEVICE_STORAGE = 'c1344062-7'
DEVICE_KITCHEN = 'c1344062-8'
DEVICE_BIOLAB = 'c1344062-9'
DEVICE_AIRLOCK = None
DEVICE_CHOICES = [
(DEVICE_ATRIUM, _('Atrium')),
(DEVICE_ANALYTIC_LAB, _('Analytic Lab')),
(DEVICE_OPERATIONS, _('Operations')),
(DEVICE_TOILET, _('Toilet')),
(DEVICE_DORMITORY, _('Dormitory')),
(DEVICE_STORAGE, _('Storage')),
(DEVICE_KITCHEN, _('Kitchen')),
(DEVICE_BIOLAB, _('Biolab'))]
datetime = models.DateTimeField(verbose_name=_('Datetime [UTC]'), db_index=True)
device = models.CharField(verbose_name=_('Sensor Location'), max_length=30, choices=DEVICE_CHOICES, db_index=True)
type = models.CharField(verbose_name=_('Type'), max_length=30, choices=TYPE_CHOICES)
value = models.DecimalField(verbose_name=_('Value'), max_digits=7, decimal_places=2, default=None)
unit = models.CharField(verbose_name=_('Unit'), max_length=15, choices=UNIT_CHOICES, null=True, blank=True, default=None)
def __str__(self) -> str:
return f'[{self.date} {self.time}] (device: {self.device}) {self.type}: {self.value} {self.unit}'
class Meta:
verbose_name = _('Data')
verbose_name_plural = _('Zwave Sensors')
@staticmethod
def add(datetime: str, device: str, type: str, value: str, unit: str):
dt = clean_datetime(datetime)
time = MissionTime().get_time_dict(from_datetime=dt)
data = {'date': time['date'],
'time': time['time'],
'device': clean_device(device),
'type': clean_type(type),
'value': clean_value(value),
'unit': clean_unit(unit)}
return ZWaveSensor.objects.update_or_create(datetime=dt, defaults=data)
from habitat.time import MissionTime
from habitat.sensors.models import ZWaveSensor
from habitat.sensors.models import clean_datetime
from habitat.sensors.models import clean_device
from habitat.sensors.models import clean_type
from habitat.sensors.models import clean_value
from habitat.sensors.models import clean_unit
dt = clean_datetime(datetime)
time = MissionTime().get_time_dict(from_datetime=dt)
data = {'date': time['date'],
'time': time['time'],
'device': clean_device(device),
'type': clean_type(type),
'value': clean_value(value),
'unit': clean_unit(unit)}
obj = ZWaveSensor.objects.update_or_create(datetime=dt, defaults=data)
obj = ZWaveSensor.add(datetime, device, type, value, unit)
6.3.6. Assignments¶
Todo
Create assignments