I have a ArrayField and want to change, but when I use .save(), object didn't update.
from django.contrib.postgres.fields import ArrayField
dates = ArrayField(models.CharField(max_length=10), size=300)
object.dates += new_list
object.save()
Related
I try to modify many instance of some model (like User model), and this changes is different (I don't want to use update QuerySet method and not works for my scenario).
For example some user need to change first_name and some user need to change last_name and get users like : all_user = User.objects.all()
I think if I use save method for each instance after change, Django sent one query for save that!
How can I save all changes to database in one query instead of use foreach on models and save that one by one?
Given the comment from #iklinac, I would thoroughly recommend implementing django's own approach to bulk updates detailed here
It's quite similar to my original answer, below, but it looks like the functionality is now built in.
# bulk_update(objs, fields, batch_size=None)
>>> objs = [
... Entry.objects.create(headline='Entry 1'),
... Entry.objects.create(headline='Entry 2'),
... ]
>>> objs[0].headline = 'This is entry 1'
>>> objs[1].headline = 'This is entry 2'
>>> Entry.objects.bulk_update(objs, ['headline'])
Original answer
There's a package called django-bulk-update which is similar to bulk create which is builtin to django.
An example of where I use this, is part of an action in an admin class;
#admin.register(Token)
class TokenAdmin(admin.ModelAdmin):
list_display = (
'id',
'type'
)
actions = (
'set_type_charity',
)
def set_type_charity(self, request, queryset):
for token in queryset:
token.type = Token.Type.CHARITY
bulk_update(
queryset,
update_fields=['type', 'modified'],
batch_size=1000
)
Usage, taken from their readme;
With manager:
import random
from django_bulk_update.manager import BulkUpdateManager
from tests.models import Person
class Person(models.Model):
...
objects = BulkUpdateManager()
random_names = ['Walter', 'The Dude', 'Donny', 'Jesus']
people = Person.objects.all()
for person in people:
person.name = random.choice(random_names)
Person.objects.bulk_update(people, update_fields=['name']) # updates only name column
Person.objects.bulk_update(people, exclude_fields=['username']) # updates all columns except username
Person.objects.bulk_update(people) # updates all columns
Person.objects.bulk_update(people, batch_size=50000) # updates all columns by 50000 sized chunks
With helper:
import random
from django_bulk_update.helper import bulk_update
from tests.models import Person
random_names = ['Walter', 'The Dude', 'Donny', 'Jesus']
people = Person.objects.all()
for person in people:
person.name = random.choice(random_names)
bulk_update(people, update_fields=['name']) # updates only name column
bulk_update(people, exclude_fields=['username']) # updates all columns except username
bulk_update(people, using='someotherdb') # updates all columns using the given db
bulk_update(people) # updates all columns using the default db
bulk_update(people, batch_size=50000) # updates all columns by 50000 sized chunks using the default db
I need to check if an object exists in the database that has at least one matching field with a field from the dictionary
Pymongo
I have this, but it doesn't work:
import pymongo
client = pymongo.MongoClient()
users_db = client['UsersDB']
users_collection = users_db['users']
def check(collection, elements):
return bool(collection.find_one(filter={'$or' : [item for item in elements.items()]}))
You are on the right track but the query needs to be valid MQL. Try:
collection.find_one(filter={'$or' : [{k:{'$eq':v}} for k,v in elements.items()]})
Hi I am writing unittest using pytest. But I am not able to mock few db functions. We are using psycopg2 for db connections and executions. Response of query returned from psycopg2 is of the type DictRow which can be accessed either by key or by index.
Ex:
response = ['prajwal', '23', 'engineer'] #Response of a query "select name, age , job from users"
>>>response[0]
'prajwal'
>>>response['name']
'prajwal'
I want to know is there any way by which we can covert dict/list to above mentioned type.
Looking at the source for psycopg2, creating a DictRow requires passing in a DictCursor object. However the only thing it uses from DictCursor appears to be an index and description attribute.
# found in lib\site-packages\psycopg2.extras.py
class DictRow(list):
"""A row object that allow by-column-name access to data."""
__slots__ = ('_index',)
def __init__(self, cursor):
self._index = cursor.index
self[:] = [None] * len(cursor.description)
The index looks like a dict with a mapping a key to an index. e.g.response['name'] = 0
The description looks like your dict that you want to convert.
If you're feeling hacky you could take advantage of duck typing and pretend you're passing in a cursor when you're just satisfying the requirements.
The only caveat is after we instantiate the DictRow, we need to populate it. Our fake cursor hack will take care of the rest.
from psycopg2.extras import DictRow
class DictRowHack:
def __init__(self, my_dict):
# we need to set these 2 attributes so that
# it auto populates our indexes
self.index = {key: i for i, key in enumerate(my_dict)}
self.description = my_dict
def dictrow_from_dict(my_dict):
# this is just a little helper function
# so you don't always need to go through
# the steps to recreate a DictRow
fake_cursor = DictRowHack(my_dict)
my_dictrow = DictRow(fake_cursor)
for k, v in my_dict.items():
my_dictrow[k] = v
return my_dictrow
response = {'name': 'prajwal', 'age': '23', 'job': 'engineer'}
my_dictrow = dictrow_from_dict(response)
print(my_dictrow[1])
print(my_dictrow['name'])
print(type(my_dictrow))
I use mongoengine and flask-restplus for API Server.
My model is here.
from datetime import datetime
from mongoengine import *
from config import DB_NAME
connect(DB_NAME)
class Board(Document):
d = datetime.now()
date = "{}-{}-{}".format(d.year, d.month, d.day)
no = SequenceField()
title = StringField(required=True)
body = StringField(required=True)
tags = ListField(StringField(unique=True))
password = StringField(required=True)
created_at = DateTimeField(default=date)
updated_at = DateTimeField(default=date)
I defined tags = ListField(StringField(unique=True)).
Because article can't got duplicated tag.
Insert tag code is here.
tag = ~some user input here~
article = Board.objects.get(no=article_no)
article.tags.append(tag)
article.save()
But when I insert the duplicated data, it stored data twice.
I want to tags has distinct data.
Why unique=True doesn't work?
Is there any solution about this issue?
Here's an explanation why does it not work. As a workaround you could use $addToSet operator provided by Mongo. It is also implemented in Mongoengine(docs) and an example usage would look like this
Board.objects(no=article_no).update_one(add_to_set__tags=tag)
where tag can be string or list of strings
Please correct my code
PS - i'm fairly new to python
class Contact:
def __init__(self,cid, email):
self.cid=cid
self.email=email
def ind(contacts):
index={}
#Code here
return index
contacts = [Contact(1,'a'),
Contact(2,'b'),
Contact(3,'c'),
Contact(4,'a')]
print(ind(contacts))
Need the output to be like -
{'a':[1,4], 'b':2, 'c':3}
The following methods create list values like:
{'a':[1,4], 'b':[2], 'c':[3]}
I can't imagine why this wouldn't be fine, but I've added a method at the end that gets your specific output.
This doesn't maintain order of the emails:
def ind(contracts):
index={}
for contract in contracts:
index.setdefault(contract.email, []).append(contract.cid)
return index
To maintain order (e.g. start with 'a'), add from collects import OrderedDict to the top of your file and then the method is:
def ind(contracts):
index = OrderedDict()
for contract in contracts:
index.setdefault(contract.email, []).append(contract.cid)
return index
The printout of index will look different, but it acts the same as a normal dict object (just with ordering).
Exact output (with ordering):
def ind(contracts):
index = OrderedDict()
for contract in contracts:
if contract.email in index:
value = index[contract.email]
if not isinstance(value, list):
index[contract.email] = [value]
index[contract.email].append(contract.cid)
else:
index[contract.email] = contract.cid
return index