I have a function that takes a class reference to create an SQL string.
I can get the class reference from globals() as long as the class name is unique.
Example call.
module_name_a.models.get_insert_string(globals()['DriverShiftPreference'])
If there are duplicate class names in different modules then I get collisions.
For example, if there is module_name_a.models.Driver and module_name_b.models.Driver then
module_name_a.models.get_insert_string(globals()['Driver'])
returns a result from module_name_b.models.Driver.
What is an effective method to get a Django class reference when there are duplicated class names in different modules?
Found using inspect gets most of the way there.
# in a module called junction
import inspect
def get_insert_string(class_reference):
fields = []
arguments = []
for field in class_reference._meta.fields:
if field.primary_key:
pass
elif field.help_text:
fields.append('"%s"' % field.help_text)
arguments.append('?')
result = 'insert into %s ( %s ) values ( %s )' % ( class_reference.filemaker_table_name, u','.join(fields), u','.join(arguments))
return result
def make_models_map_from_module(module_):
result = {}
for item in inspect.getmembers(module_.models):
key = item[0]
value = item[1]
if key == '__builtins__':
break
else:
result[key] = value
return result
Sample usage:
import junction
import depot_maestro
depot_maestro_model_map = junction.models.make_models_map_from_module(depot_maestro)
junction.models.get_insert_string(depot_maestro_model_map['Driver'])
u'insert into driver ( "DEPOT_ID","uuid","ABN_number","account_name","address_1","advance_payment_days","bank_account","barred_flag","biometric_print","bsb","change_log","comm_fixed_percent","company","contract_end_date","contract_fixed","contract_notice_period","contract_start_date","contract_terms","country","date_activated","DOB","default_roster_template_id","EFT_code","email","external_id","fax","first_name","fuel_pin","fuel_split_percent","gender","is_owner","known_as","last_contacted","middle_name","nationality","Next_of_kin","next_of_kin_mobile","Next_of_kin_phone","next_of_kin_relationship","next_of_kin_work","passport","password","pay_in_choice","phone","pref_age","pref_body_type","pref_name_display","pref_transmission","remit_gst_for_ATO_who_remits","roster_template_id","status","surname","toll_serial_no","tsl_owner","unreliable_flag","www_LastKnown_GPS","www_LastKnown_Status","www_LastKnown_Timestamp","creationAccount","creationTimeStamp","modificationAccount","modificationTimeStamp" ) values ( ?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,? )'
Found a much simpler way. Just pass in the model.
Example.
junction.models.get_insert_string(depot_maestro.models.Group)
which returns
insert into groups ( "DEPOT_ID","uuid","Notes","Percentage","abn","address","admin_fee","bank_details","bookings_percent","creationAccount","creationTimeStamp","email","fax","group_account_name","group_colour","group_logo","group_logo_2","group_name","group_number","group_service_mark_as_paid","gst","message","meter","modificationAccount","modificationTimeStamp","omit_from_group_reports","parts_at_cost","phone","remit_all_cash","rollover_amount","roster_group","sort_order","vehicle_fk" ) values ( ?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,? )'
I have a model that has a type and value, based on the type I want to change the sign of the number to negative (Without changing it in the database)
class Foo(models.Model):
EARNING_CATEGORY = 'E'
DEDUCTION_CATEGORY = 'D'
CATEGORY_CHOICES = (
(EARNING_CATEGORY, 'Earning'),
(DEDUCTION_CATEGORY, 'Deduction'),
)
name = models.CharField(max_length=50)
category = models.CharField(max_length=1, choices=CATEGORY_CHOICES)
value = models.FloatField()
Now in order to aggregate over Foo I need to consider that values with category = D should be negative so I get the real sum.
What I tried so far is to change the sign during the save() method, but I don't want to show it to the user as negative in the application. So the only way I came up with is to calculate in a method using a for loop.
class Account(models.Model):
# feilds
def sum(self):
items = self.foo_set.all()
sum = 0
for i in items:
if i.category == Foo.DEDUCTION_CATEGORY:
sum -= i.value
else:
sum += i.value
return sum
You can annotate the current sign during your query like this:
from django.db.models import Case, Value as V, F, FloatField, When
items = self.foo_set.annotate(fixed_value=Case(
When(category=Foo.DEDUCTION_CATEGORY, then=V('-1')*F('value')),
default=F('value'),
output_field=FloatField())
).all()
So during annotation we do a condition check and if our category is equal to 'D', we change sign of value field, and then do your aggregation on fixed_value field.
And here's more info:
https://docs.djangoproject.com/en/1.9/ref/models/conditional-expressions/#case
I have some server side processing of some data (client-side library = jQuery DataTables)
I am using POST as my ajax method. In my Flask webapp, I can access the POST data with request.values
The data type / structure of request.values is werkzeug.datastructures.CombinedMultiDict
If the user wants to sort a column, the request contains a key called action with a value of filter (note the below printouts are obtained with for v in request.values: print v, request.values[v])
...
columns[7][data] role
columns[8][search][regex] false
action filter
columns[10][name]
columns[3][search][value]
...
all the column names are also contained in the request as keys. The columns that have search terms will have the search string as a value for the column name key (as opposed to empty for columns with no search term entered. So, If I want to search for firstname containing bill, I would see the following in my request
columns[7][searchable] true
...
columns[6][name]
firstname bill
columns[0][search][value]
columns[2][searchable] true
...
columns[5][data] phone
role
columns[10][data] registered_on
...
columns[0][searchable] true
email
columns[7][orderable] true
...
columns[2][search][value]
Notice how role and email are empty. So my code below is very non-DRY
rv = request.values
if rv.get('action') == 'filter':
if len(rv.get('firstname')):
q = q.filter(User.firstname.ilike('%{0}%'.format(rv.get('firstname'))))
if len(rv.get('lastname')):
q = q.filter(User.lastname.ilike('%{0}%'.format(rv.get('lastname'))))
if len(rv.get('username')):
q = q.filter(User.username.ilike('%{0}%'.format(rv.get('username'))))
if len(rv.get('email')):
q = q.filter(User.email.ilike('%{0}%'.format(rv.get('email'))))
if len(rv.get('phone')):
q = q.filter(User.phone.ilike('%{0}%'.format(rv.get('phone'))))
if len(rv.get('region')):
q = q.filter(User.region.name.ilike('%{0}%'.format(rv.get('region'))))
if len(rv.get('role')):
q = q.filter(User.role.name.ilike('%{0}%'.format(rv.get('role'))))
if len(rv.get('is_active')):
q = q.filter(User.is_active_ == '{0}'.format(rv.get('is_active')))
if len(rv.get('is_confirmed')):
q = q.filter(User.is_confirmed == '{0}'.format(rv.get('is_confirmed')))
if len(rv.get('registered_on_from')):
fdate = datetime.strptime(rv.get('registered_on_from'), '%Y-%m-%d')
q = q.filter(User.registered_on > fdate)
if len(rv.get('registered_on_to')):
tdate = datetime.strptime(rv.get('registered_on_to'), '%Y-%m-%d')
q = q.filter(User.registered_on < tdate)
I was building the sorting functionality, and I found the following statement that greatly simplified my life (see this answer)
q = q.order_by('{name} {dir}'.format(name=sort_col_name, dir=sort_dir))
I was wondering if there was a way to simplify this set of filtering queries like the above sorting code since I will have to do this for many other models.
This should help:
from sqlalchemy import inspect
from sqlalchemy.sql.sqltypes import String,Boolean
def filter_model_by_request(qry,model,rv):
if rv.get('action') == 'filter':
mapper = inspect(model).attrs # model mapper
col_names = list(set([c.key for c in mapper]) & set(rv.keys()))
# col_names is a list generated by intersecting the request values and model column names
for col_name in col_names:
col = mapper[col_name].columns[0]
col_type = type(col.type)
if col_type == String: # filter for String
qry = qry.filter(col.ilike('%{0}%'.format(rv.get(col_name))))
elif col_type == Boolean: # filter for Boolean
qry = qry.filter(col == '{0}'.format(rv.get(col_name)))
return qry
Example call (I used it with a #app.before_request and a cURL call to verify):
qry = db.session.query(User)
print filter_model_by_request(qry,User,request.values).count()
The date range filtering is not included in the function, add this feature if you wish, your code is fine for that purpose.
side note: be careful with the bigger/smaller operators for the dates. You're excluding the actual requested dates. Use <= or >= to include dates in filtering action. It's always a pitfall for me..
I'm trying to get the next and previous objects of a comic book issue. Simply changing the id number or filtering through date added is not going to work because I don't add the issues sequentially.
This is how my views are setup and it WORKS for prev_issue and does return the previous object, but it returns the last object for next_issue and I do not know why.
def issue(request, issue_id):
issue = get_object_or_404(Issue, pk=issue_id)
title = Title.objects.filter(issue=issue)
prev_issue = Issue.objects.filter(title=title).filter(number__lt=issue.number)[0:1]
next_issue = Issue.objects.filter(title=title).filter(number__gt=issue.number)[0:1]
Add an order_by clause to ensure it orders by number.
next_issue = Issue.objects.filter(title=title, number__gt=issue.number).order_by('number').first()
I know this is a bit late, but for anyone else, django does have a nicer way to do this, see https://docs.djangoproject.com/en/1.7/ref/models/instances/#django.db.models.Model.get_previous_by_FOO
So the answer here would be something something like
next_issue = Issue.get_next_by_number(issue, title=title)
Django managers to do that with a bit of meta class cleaverness.
If it's required to find next and previous objects ordered by field values that can be equal and those fields are not of Date* type, the query gets slightly complex, because:
ordering on objects with same values limiting by [:1] will always produce same result for several objects;
object can itself be included in resulting set.
Here's are querysets that also take into account the primary keys to produce a correct result (assuming that number parameter from OP is not unique and omitting the title parameter as it's irrelevant for the example):
Previous:
prev_issue = (Issue.objects
.filter(number__lte=issue.number, id__lt=instance.id)
.exclude(id=issue.id)
.order_by('-number', '-id')
.first())
Next:
next_issue = (Issue.objects
.filter(number__gte=issue.number, id__gt=instance.id)
.exclude(id=issue.id)
.order_by('number', 'id')
.first())
from functools import partial, reduce
from django.db import models
def next_or_prev_instance(instance, qs=None, prev=False, loop=False):
if not qs:
qs = instance.__class__.objects.all()
if prev:
qs = qs.reverse()
lookup = 'lt'
else:
lookup = 'gt'
q_list = []
prev_fields = []
if qs.query.extra_order_by:
ordering = qs.query.extra_order_by
elif qs.query.order_by:
ordering = qs.query.order_by
elif qs.query.get_meta().ordering:
ordering = qs.query.get_meta().ordering
else:
ordering = []
ordering = list(ordering)
if 'pk' not in ordering and '-pk' not in ordering:
ordering.append('pk')
qs = qs.order_by(*ordering)
for field in ordering:
if field[0] == '-':
this_lookup = (lookup == 'gt' and 'lt' or 'gt')
field = field[1:]
else:
this_lookup = lookup
q_kwargs = dict([(f, get_model_attr(instance, f))
for f in prev_fields])
key = "%s__%s" % (field, this_lookup)
q_kwargs[key] = get_model_attr(instance, field)
q_list.append(models.Q(**q_kwargs))
prev_fields.append(field)
try:
return qs.filter(reduce(models.Q.__or__, q_list))[0]
except IndexError:
length = qs.count()
if loop and length > 1:
return qs[0]
return None
next_instance = partial(next_or_prev_instance, prev=False)
prev_instance = partial(next_or_prev_instance, prev=True)
note that do not use object.get(pk=object.pk + 1) these sorts of things, IntegrityError occurs if object at that pk is deleted, hence always use a query set
for visitors:
''' Useage '''
"""
# Declare our item
store = Store.objects.get(pk=pk)
# Define our models
stores = Store.objects.all()
# Ask for the next item
new_store = get_next_or_prev(stores, store, 'next')
# If there is a next item
if new_store:
# Replace our item with the next one
store = new_store
"""
''' Function '''
def get_next_or_prev(models, item, direction):
'''
Returns the next or previous item of
a query-set for 'item'.
'models' is a query-set containing all
items of which 'item' is a part of.
direction is 'next' or 'prev'
'''
getit = False
if direction == 'prev':
models = models.reverse()
for m in models:
if getit:
return m
if item == m:
getit = True
if getit:
# This would happen when the last
# item made getit True
return models[0]
return False
original author
Usage
# you MUST call order by to pass in an order, otherwise QuerySet.reverse will not work
qs = Model.objects.all().order_by('pk')
q = qs[0]
prev = get_next_or_prev(qs, q, 'prev')
next = get_next_or_prev(qs, q, 'next')
next_obj_id = int(current_obj_id) + 1
next_obj = Model.objects.filter(id=next_obj_id).first()
prev_obj_id= int(current_obj_id) - 1
prev_obj = Model.objects.filter(id=prev_obj_id).first()
#You have nothing to loose here... This works for me