Peewee module basic use -orm

github： ​ ​ ​ ​https://github.com/coleifer/peewee​​​​

Official documents ：​ ​ ​ ​http://docs.peewee-orm.com/en/latest/index.html#​​​​

Defining models is similar to Django or SQLAlchemy

Logical operators

The operator	Meaning	Example
​​&​​	AND	​​(User.is_active == True) & (User.is_admin == True)​​
| (pipe)	OR	(User.is_admin) | (User.is_superuser)
​​~​​	NOT (unary negation)	​​~(User.username << ['foo', 'bar', 'baz'])​​

Expression conversion

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        Method  Meaning
        
.in_(value) IN lookup (identical to <<).
        
.not_in(value)  NOT IN lookup.
        
.is_null(is_null)   IS NULL or IS NOT NULL. Accepts boolean param.
        
.contains(substr)   Wild-card search for substring.
        
.startswith(prefix) Search for values beginning with prefix.
        
.endswith(suffix)   Search for values ending with suffix.
        
.between(low, high) Search for values between low and high.
        
.regexp(exp)    Regular expression match (case-sensitive).
        
.iregexp(exp)   Regular expression match (case-insensitive).
        
.bin_and(value) Binary AND.
        
.bin_or(value)  Binary OR.
        
.concat(other)  Concatenate two strings or objects using ||.
        
.distinct() Mark column for DISTINCT selection.
        
.collate(collation) Specify column with the given collation.
        
.cast(type) Cast the value of the column to the given type.
       
       

        
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        in_(): IN
        
not_in(): NOT IN
        
regexp(): REGEXP
        
is_null(True/False): IS NULL or IS NOT NULL
        
contains(s): LIKE %s%
        
startswith(s): LIKE s%
        
endswith(s): LIKE %s
        
between(low, high): BETWEEN low AND high
        
concat(): ||
       
       

        
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give an example ：

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        SELECT * FROM user WHERE username not like "%admin%"
        
# ~(User.username.contains('admin'))
        

        
SELECT * FROM user WHERE LENGTH(username)>45
        
# fn.length(User.username) > 45
       
       

        
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Reference resources ： ​ ​http://docs.peewee-orm.com/en/latest/peewee/query_operators.html​​

call sql function

Use fn

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        query = (User
        
         .select(User.username, fn.COUNT(Tweet.id).alias('ct'))
        
         .join(Tweet, JOIN.LEFT_OUTER, on=(User.id == Tweet.user_id))
        
         .group_by(User.username)
        
         .order_by(fn.COUNT(Tweet.id).desc()))
       
       

        
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Reference resources ：​ ​https://peewee.readthedocs.io/en/latest/peewee/api.html#fn​​

The following code refers to the official example

Sample code ：

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        # —*— coding: utf-8 —*—
        

        
from peewee import *
        
import datetime
        
from chinesename import chinesename
        

        
# py2 Solve coding problems 
        
import sys
        
reload(sys)
        
sys.setdefaultencoding("utf-8")
        

        
#  Set up the database 
        
db = SqliteDatabase("demo.db")
        

        
class BaseModel(Model):
        
    class Meta:
        
        database = db
        

        
#  Define data table 
        
class User(BaseModel):
        
    name = CharField(unique=True)
        

        
    def __str__(self):
        
        return "[user] id: %d  name: %s"%(self.id, self.name)
        

        
class Tweet(BaseModel):
        
    user = ForeignKeyField(User, related_name ="tweets")
        
    message = TextField()
        
    created_date = DateTimeField(default=datetime.datetime.now)
        
    is_published = BooleanField(default=True)
        

        
    def __str__(self):
        
        return "[tweet] id: %d  name: %s" % (self.id, self.user.name)
        

        
#  Create data table 
        
db.connect()
        
db.create_tables([User, Tweet], safe=True)
        
db.close()
        

        
#  Add data 
        
def add_data():
        
    cn = chinesename.ChineseName()
        
    for i in range(100):
        
        user = User(name=cn.getName())
        
        user.save()
        

        
        User.create(name=cn.getName())
        

        
        Tweet.create(user=user, message="hello world")
        

        
# add_data()
        

        
print datetime.datetime.now()
        
print datetime.date.today()
        

        
#  Inquire about 
        
ret = User.get(User.name==" Shen from ")
        
if ret: print ret
        

        

        
usernames = [" Ma Niang ", " Shen from "]
        
users = User.select().where(User.name.in_(usernames))
        
for user in users:
        
    print user
        

        
tweets = Tweet.select().where(Tweet.user.in_(users))
        
for tweet in tweets:
        
    print tweet
        

        

        
tweets = Tweet.select().join(User).where(User.name.in_(usernames))
        
for tweet in tweets:
        
    print tweet
        

        
count = (Tweet
        
         .select()
        
         .where(
        
            (Tweet.created_date >= datetime.date.today())&
        
            (Tweet.is_published == True))
        
         .count())
        

        
print count
        

        
#  Pagination  page 3 (users 41-60)
        
users = User.select().order_by(User.name).paginate(3, 20)
        
for user in users:
        
    print user
        

        
#  to update 
        
query = User.update(name=" Simon blow snow ").where(User.id==1)
        
query.execute()
        

        
#  Delete 
        
query = User.delete().where(User.id==2)
        
query.execute()
       
       

        
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