導入 Django 以架設物聯網中的資料紀錄網站¶

class Group(models.Model):
    name = models.CharField(max_length=150, unique=True)
    permissions = models.ManyToManyField(Permission, blank=True)
class User(models.Model):
    username = models.CharField(max_length=150)
    password = models.CharField(max_length=128)
    first_name = models.CharField(max_length=30, blank=True)
    last_name = models.CharField(max_length=150, blank=True)
    email = models.EmailField(blank=True)
    is_active = models.BooleanField(default=False)
    is_staff = models.BooleanField(default=False)
    is_superuser = models.BooleanField(default=False)
    date_joined = models.DateTimeField(auto_now_add=True)
    last_login = models.DateTimeField()
    groups = models.ManyToManyField(Group, blank=True)
    user_permissions = models.ManyToManyField(Permission, blank=True)

In [1]: from django.contrib.auth.models import User, Group
In [2]: u1 = User(username='user1', email='user1@ho600.com')
In [3]: u1.save()
In [4]: u2 = User(username='user2', email='user2@ho600.com')
In [5]: u2.save()
In [6]: g1 = Group(name='Normal User')
In [7]: g1.save()
In [8]: u1.groups.add(g1)
In [9]: g1.user_set.add(u2)
In [10]: for u in User.objects.all().order_by('id')[:2]:
    ...:     print("{}, {}".format(u.id, u.username))
1, user1
2, user2
In [11]: from django.db.models import Q
In [12]: for u in g1.user_set.all().filter(
    ...:     username__in=['user1', 'user2']
    ...:     ).filter(Q(id=1, username='user1')
    ...:              |Q(id=2, username='user2')
    ...:             ).order_by('-id'):
    ...:     print(u.username)
2 user2
1 user1
In [13]: u2.delete()
In [14]: for u in g1.user_set.filter(username__isnull=False):
    ...:     print(u.username)
user1

class EndSpot(models.Model):
    topic = models.CharField(max_length=150, unique=True)
    note = models.TextField()

    class Meta:
        permissions = (
            ('add_flowdata_under_this_end_spot',
             'Add FlowData records under This EndSpot'),
        )

class FlowData(models.Model):
    end_spot = models.ForeignKey(EndSpot, on_delete=models.CASCADE)
    timestamp = models.DecimalField(max_digits=20, decimal_places=6, db_index=True)
    value = models.FloatField() #IFNO: in some cases, DecimalField is better
    create_time = models.DateTimeField(auto_now_add=True, db_index=True)

import requests
def post_data(*args, **kw):
    msg = args[0]
    url = 'http://127.0.0.1:8000/api/v1/flowdata/?format=json'
    topic_mapping = {
        "ho600/office/power1": 1,
    }
    data = {
        "end_spot": topic_mapping[msg.topic],
        "timestamp": msg.payload.get('timestamp', ''),
        "value": msg.payload.get('value', ''),
    }
    res = requests.post(url, data=data)
    print(res.text)
    #INFO: {"id":5,
    #       "resource_uri":
    #           "http://127.0.0.1:8000/api/v1/flowdata/5/?format=json",
    #       "timestamp":"123.123456","value":4.1,
    #       "create_time":"2020-01-17T18:11:42.967727Z","end_spot":1}