feat: 新增技能扩展N9一章相关示例源码

code/newsletter/N9/crud/pw_update.py

@@ -0,0 +1,77 @@
+import pathlib
+from datetime import datetime
+
+import peewee as pw
+
+db_url = pathlib.Path(__file__).parents[1].joinpath("./mydb.sqlite3")
+db = pw.SqliteDatabase(db_url)
+
+
+class BaseModel(pw.Model):
+    class Meta:
+        database = db
+
+
+class User(BaseModel):
+    uid = pw.AutoField()
+    username = pw.CharField(max_length=10)
+
+    def __repr__(self) -> str:
+        return f"User<uid={self.uid}, username={self.username}>"
+
+    __str__ = __repr__
+
+
+class Weibo(BaseModel):
+    wid = pw.AutoField()
+    content = pw.TextField()
+    timestamp = pw.DateTimeField(default=datetime.now)
+    user = pw.ForeignKeyField(User, backref="user", field="uid")
+
+
+class Likes(BaseModel):
+    user = pw.ForeignKeyField(User, backref="likes", field="uid")
+    weibo = pw.ForeignKeyField(Weibo, backref="likes", field="wid")
+
+    class Meta:
+        primary_key = pw.CompositeKey("user", "weibo")
+
+
+def main():
+
+    # --------------
+    # inplace change
+    user = User.select().where(User.username.startswith("Steve")).get()
+    print(f"before updating: {user}")
+
+    user.username = user.username.lower()
+    user.save()
+    user = User.select().where(User.username.startswith("Steve")).get()
+    print(f"after updating: {user}")
+
+    # -------
+    # update
+    user = User.select().where(User.username == "100gle").get()
+    print(f"before updating: {user}")
+
+    query = User.update(username="100GLE").where(User.username == "100gle")
+    query.execute()
+
+    user = User.select().where(User.username.startswith("100")).get()
+    print(f"after updating: {user}")
+
+    # --------------------
+    # update multiple rows
+    users = User.select().where(User.username.in_(["Bill Gates", "Larry Page"]))
+    print(f"before updating: {list(users)}")
+    u1, u2 = users
+    u1.username = u1.username.lower()
+    u2.username = u2.username.lower()
+    User.bulk_update([u1, u2], fields=[User.username])
+
+    users = user.select().where(User.username.in_(["bill gates", "larry page"]))
+    print(f"after updating: {list(users)}")
+
+
+if __name__ == '__main__':
+    main()