I have a Django form setup using GET method. Each value corresponds to attributes of a Django model. What would be the most elegant way to generate the query? Currently this is what I do in the view:
def search_items(request):
if 'search_name' in request.GET:
query_attributes = {}
query_attributes['color'] = request.GET.get('color', '')
if not query_attributes['color']: del query_attributes['color']
query_attributes['shape'] = request.GET.get('shape', '')
if not query_attributes['shape']: del query_attributes['shape']
items = Items.objects.filter(**query_attributes)
But I'm pretty sure there's a better way to go about it.
You could do it with a list comp and and "interested params" set:
def search_items(request):
if 'search_name' in request.GET:
interested_params = ('color', 'shape')
query_attrs = dict([(param, val) for param, val in request.GET.iteritems()
if param in interested_params and val])
items = Items.objects.filter(**query_attrs)
Just for fun (aka don't actually do this) you could do it in one line:
def search_items(request):
items = Items.objects.filter(
**dict([(param, val) for param, val in request.GET.iteritems()
if param in ('color', 'shape') and val])
) if 'search_name' in request.GET else None
well, the basic way you are approaching the problem seems sound, but the way you wrote it out looks a little funny. I'd probably do it this way:
def search_items(request):
if 'search_name' in request.GET:
query_attributes = {}
color = request.GET.get('color', '')
if color:
query_attributes['color'] = color
shape = request.GET.get('shape', '')
if shape:
query_attributes['shape'] = shape
items = Items.objects.filter(**query_attributes)
If you want it to be fully dynamic, you can use a little bit of model introspection to find out what fields you can actually query, and filter only using those.
Though, this solution won't allow you to use __lookups in GET parameters, don't know if you need it.
def search_items(request):
if 'search_name' in request.GET:
all_fields = Items._meta.get_all_field_names()
filters = [(k, v) for k, v in request.GET.items() if k in all_fields]
items = Items.objects.filter(*filters)
def search_items(request):
try:
items = Items.objects.filter(**dict([
(F, request.GET[F]) for F in ('color', 'shape')
]))
except KeyError:
raise Http404
Suppose 'color' and 'shape' are required GET params. Predefined tuple of filtering params is prefered because of security reasons.
Related
I'm trying to programmatically set a value in a dictionary, potentially nested, given a list of indices and a value.
So for example, let's say my list of indices is:
['person', 'address', 'city']
and the value is
'New York'
I want as a result a dictionary object like:
{ 'Person': { 'address': { 'city': 'New York' } }
Basically, the list represents a 'path' into a nested dictionary.
I think I can construct the dictionary itself, but where I'm stumbling is how to set the value. Obviously if I was just writing code for this manually it would be:
dict['Person']['address']['city'] = 'New York'
But how do I index into the dictionary and set the value like that programmatically if I just have a list of the indices and the value?
Python
Something like this could help:
def nested_set(dic, keys, value):
for key in keys[:-1]:
dic = dic.setdefault(key, {})
dic[keys[-1]] = value
And you can use it like this:
>>> d = {}
>>> nested_set(d, ['person', 'address', 'city'], 'New York')
>>> d
{'person': {'address': {'city': 'New York'}}}
I took the freedom to extend the code from the answer of Bakuriu. Therefore upvotes on this are optional, as his code is in and of itself a witty solution, which I wouldn't have thought of.
def nested_set(dic, keys, value, create_missing=True):
d = dic
for key in keys[:-1]:
if key in d:
d = d[key]
elif create_missing:
d = d.setdefault(key, {})
else:
return dic
if keys[-1] in d or create_missing:
d[keys[-1]] = value
return dic
When setting create_missing to True, you're making sure to only set already existing values:
# Trying to set a value of a nonexistent key DOES NOT create a new value
print(nested_set({"A": {"B": 1}}, ["A", "8"], 2, False))
>>> {'A': {'B': 1}}
# Trying to set a value of an existent key DOES create a new value
print(nested_set({"A": {"B": 1}}, ["A", "8"], 2, True))
>>> {'A': {'B': 1, '8': 2}}
# Set the value of an existing key
print(nested_set({"A": {"B": 1}}, ["A", "B"], 2))
>>> {'A': {'B': 2}}
Here's another option:
from collections import defaultdict
recursivedict = lambda: defaultdict(recursivedict)
mydict = recursivedict()
I originally got this from here: Set nested dict value and create intermediate keys.
It is quite clever and elegant if you ask me.
First off, you probably want to look at setdefault.
As a function I'd write it as
def get_leaf_dict(dct, key_list):
res=dct
for key in key_list:
res=res.setdefault(key, {})
return res
This would be used as:
get_leaf_dict( dict, ['Person', 'address', 'city']) = 'New York'
This could be cleaned up with error handling and such. Also using *args rather than a single key-list argument might be nice; but the idea is that
you can iterate over the keys, pulling up the appropriate dictionary at each level.
Here is my simple solution: just write
terms = ['person', 'address', 'city']
result = nested_dict(3, str)
result[terms] = 'New York' # as easy as it can be
You can even do:
terms = ['John', 'Tinkoff', '1094535332'] # account in Tinkoff Bank
result = nested_dict(3, float)
result[terms] += 2375.30
Now the backstage:
from collections import defaultdict
class nesteddict(defaultdict):
def __getitem__(self, key):
if isinstance(key, list):
d = self
for i in key:
d = defaultdict.__getitem__(d, i)
return d
else:
return defaultdict.__getitem__(self, key)
def __setitem__(self, key, value):
if isinstance(key, list):
d = self[key[:-1]]
defaultdict.__setitem__(d, key[-1], value)
else:
defaultdict.__setitem__(self, key, value)
def nested_dict(n, type):
if n == 1:
return nesteddict(type)
else:
return nesteddict(lambda: nested_dict(n-1, type))
The dotty_dict library for Python 3 can do this. See documentation, Dotty Dict for more clarity.
from dotty_dict import dotty
dot = dotty()
string = '.'.join(['person', 'address', 'city'])
dot[string] = 'New York'
print(dot)
Output:
{'person': {'address': {'city': 'New York'}}}
Use these pair of methods
def gattr(d, *attrs):
"""
This method receives a dict and list of attributes to return the innermost value of the give dict
"""
try:
for at in attrs:
d = d[at]
return d
except:
return None
def sattr(d, *attrs):
"""
Adds "val" to dict in the hierarchy mentioned via *attrs
For ex:
sattr(animals, "cat", "leg","fingers", 4) is equivalent to animals["cat"]["leg"]["fingers"]=4
This method creates necessary objects until it reaches the final depth
This behaviour is also known as autovivification and plenty of implementation are around
This implementation addresses the corner case of replacing existing primitives
https://gist.github.com/hrldcpr/2012250#gistcomment-1779319
"""
for attr in attrs[:-2]:
# If such key is not found or the value is primitive supply an empty dict
if d.get(attr) is None or isinstance(d.get(attr), dict):
d[attr] = {}
d = d[attr]
d[attrs[-2]] = attrs[-1]
Here's a variant of Bakuriu's answer that doesn't rely on a separate function:
keys = ['Person', 'address', 'city']
value = 'New York'
nested_dict = {}
# Build nested dictionary up until 2nd to last key
# (Effectively nested_dict['Person']['address'] = {})
sub_dict = nested_dict
for key_ind, key in enumerate(keys[:-1]):
if not key_ind:
# Point to newly added piece of dictionary
sub_dict = nested_dict.setdefault(key, {})
else:
# Point to newly added piece of sub-dictionary
# that is also added to original dictionary
sub_dict = sub_dict.setdefault(key, {})
# Add value to last key of nested structure of keys
# (Effectively nested_dict['Person']['address']['city'] = value)
sub_dict[keys[-1]] = value
print(nested_dict)
>>> {'Person': {'address': {'city': 'New York'}}}
This is a pretty good use case for a recursive function. So you can do something like this:
def parse(l: list, v: str) -> dict:
copy = dict()
k, *s = l
if len(s) > 0:
copy[k] = parse(s, v)
else:
copy[k] = v
return copy
This effectively pops off the first value of the passed list l as a key for the dict copy that we initialize, then runs the remaining list through the same function, creating a new key under that key until there's nothing left in the list, whereupon it assigns the last value to the v param.
This is much easier in Perl:
my %hash;
$hash{"aaa"}{"bbb"}{"ccc"}=1; # auto creates each of the intermediate levels
# of the hash (aka: dict or associated array)
I have a problem filtering the data and showing the result in a table...
In my template I have some inputs that I send input values with ajax and then i get the value using request.POST.get() in my views. The problem appears when some fields are empty I receive an error "Cannot use None as a query value"
I want to do something like this but i cannot find a solution
ex. when the request.POST.get is empty that Q to be ignored
Can anyone help me?
Thanks and sorry for my english
This is my code in my views.py
def api(request):
a = request.POST.get('a')
b = request.POST.get('b')
c = request.POST.get('c')
d = request.POST.get('d')
e = request.POST.get('e')
f = request.POST.get('f')
g = request.POST.get('g')
h = request.POST.get('h')
raport = Test.objects.filter(
Q(data_test__year__gte=a) &
Q(data_test__year__lte=b) &
Q(data_in__isnull=c) &
Q(data_out__isnull=d) &
Q(adress__fieldone=e) &
Q(adress__fieldtwo=f) &
Q(categoru=g) &
Q(stare=h) &
Q(medic=i)
)
serializer = TestSerializer(raport, many=True)
return JsonResponse(serializer.data, safe=False)
We can make a function that creates a Q-object [Django-doc] for only non-None values, like:
from django.db.models import Q
def q_without_none(**kwargs):
return Q(**{k: v for k, v in kwargs.items() if v is not None})
or if you want to exclude the empty string as well:
from django.db.models import Q
def q_without_empty(**kwargs):
return Q(**{k: v for k, v in kwargs.items() if v not in (None, '')})
Then we can construct the query like:
raport_pacient = Pacient.objects.filter(
q_without_none(
data_creare_pacient__year__gte=de_la,
data_creare_pacient__year__lte=pana_la,
data_iesire__isnull=iesit,
data_deces__isnull=iesit,
adresa_pacient__judet__nume_judet=judet,
adresa_pacient__localitate__nume_localitate=localitate,
categorie=categorie,
stare_civila=stare_civila,
medic=request.user.medic
)
)
Note: although not really your question, using a JsonResponse with safe=False is, like the name suggests, not very safe. There have been exploits with lists for JSON, so it is usually better to define a dictionary at the top level, for example like:
return JsonResponse({'data': serializer.data})
In Django admin, if I want to display a list of Iron and their respective formatted weights, I would have to do this.
class IronAdmin(admin.ModelAdmin):
model = Iron
fields = ('weight_formatted',)
def weight_formatted(self, object):
return '{0:.2f} Kg'.format(object.weight)
weight_formatted.short_description = 'Weight'
I.e: 500.00 Kg
The problem with this however is that I would have to write a method for every field that I want to format, making it redundant when I have 10 or more objects to format.
Is there a method that I could override to "catch" these values and specify formatting before they get rendered onto the html? I.e. instead of having to write a method for each Admin class, I could just write the following and have it be formatted.
class IronAdmin(admin.ModelAdmin):
model = Iron
fields = ('weight__kg',)
def overriden_method(field):
if field.name.contains('__kg'):
field.value = '{0:.2f} Kg'.format(field.value)
I.e: 500.00 Kg
After hours scouring the source , I finally figured it out! I realize this isn't the most efficient code and it's probably more trouble than it's worth in most use cases but it's enough for me. In case anyone else needs a quick and dirty way to do it:
In order to automate it, I had to override django.contrib.admin.templatetags.admin_list.result_list with the following:
def result_list_larz(cl):
"""
Displays the headers and data list together
"""
resultz = list(results(cl)) # Where we override
""" Overriding starts here """
""" Have to scrub the __kg's as result_header(cl) will error out """
for k in cl.list_display:
cl.list_display[cl.list_display.index(k)] = k.replace('__kg','').replace('__c','')
headers = list(result_headers(cl))
num_sorted_fields = 0
for h in headers:
if h['sortable'] and h['sorted']:
num_sorted_fields += 1
return {'cl': cl,
'result_hidden_fields': list(result_hidden_fields(cl)),
'result_headers': headers,
'num_sorted_fields': num_sorted_fields,
'results': resultz}
Then overriding results(cl)'s call to items_for_result() wherein we then override its call to lookup_field() as follows:
def lookup_field(name, obj, model_admin=None):
opts = obj._meta
try:
f = _get_non_gfk_field(opts, name)
except (FieldDoesNotExist, FieldIsAForeignKeyColumnName):
# For non-field values, the value is either a method, property or
# returned via a callable.
if callable(name):
attr = name
value = attr(obj)
elif (model_admin is not None and
hasattr(model_admin, name) and
not name == '__str__' and
not name == '__unicode__'):
attr = getattr(model_admin, name)
value = attr(obj)
""" Formatting code here """
elif '__kg' in name or '__c' in name: # THE INSERT FOR FORMATTING!
actual_name = name.replace('__kg','').replace('__c', '')
value = getattr(obj, actual_name)
value = '{0:,.2f}'.format(value)
prefix = ''
postfix = ''
if '__kg' in name:
postfix = ' Kg'
elif '__c' in name:
prefix = 'P'
value = '{}{}{}'.format(prefix, value, postfix)
attr = value
else:
attr = getattr(obj, name)
if callable(attr):
value = attr()
else:
value = attr
f = None
""" Overriding code END """
else:
attr = None
value = getattr(obj, name)
return f, attr, value
I'm generating a form based on meta data in the following manner
class MeasureForm(forms.Form):
def __init__(self,measure_id,*args,**kwrds):
super(MeasureForm,self).__init__(*args,**kwrds)
m = Measure.objects.get(pk=measure_id);
if (m):
self.fields["measure_id"] = forms.IntegerField(initial = m.id , widget=forms.HiddenInput())
for mp in MeasureParameters.objects.filter(measure = m):
# get the NVL'ed copy of the parameter
p = mp.get_parameter_for_measure()
if not p.is_modifiable:
# the file has a constant value
if (p.values and p.default): # contant must have both values and default index
value_ = p.values[p.values.keys()[p.default-1]];
self.fields[p.name] = forms.IntegerField(label = p.description , initial = value_);
self.fields[p.name].widget.attrs['readonly'] = True;
else:
raise Exception("Parameter set as unmodifiable but has no value. [measure: %s, parameter: %s, measureparameter %s]"
% (measure_id , p.id , mp.__unicode__()))
elif (p.values):
# convert hstore dict to list of tuples for the choices to read
values_ = [(v, k) for k, v in p.values.iteritems()];
# set default if exists , else take the first item
default_ = values_[p.default-1][0] if p.default else values_[0][0]
self.fields[p.name] = forms.ChoiceField(label = p.description , choices = values_ , initial = default_)
else:
self.fields[p.name] = forms.IntegerField(label = p.description)
if (not p.is_visible):
self.fields[p.name].widget = forms.HiddenInput()
else:
raise Exception ("Could not find measure. [measure %s]" % (measure_id));
This is my view
def index(request,measure_id = None):
owners = Owner.objects.all()
form = None
result = None
title = None
# handle the form
if request.method == 'POST': # the form has been submitted
form = MeasureForm(request.POST)
if form.is_valid(): # All validation rules pass
result = 100;
else:
if (measure_id):
title = Measure.objects.get(pk=measure_id).name;
# make an unbound form
form = MeasureForm(measure_id)
return render(request, 'calc/index.html' ,
{'owners' : owners,
'form' : form ,
'title' : title ,
'result' : result})
I followed this tutorial.
I'm running into a problem when i issue submit back to the index view. i get the following error
int() argument must be a string or a number, not 'QueryDict'
I can see in the dump that it's fail in this line
m = Measure.objects.get(pk=measure_id);
So I looked around and found this post . I tried to change the call to the form like this
form = MeasureForm(request.POST, measure_id = request.POST.get('measure_id'))
and i got the following error
__init__() got multiple values for keyword argument 'measure_id'
My first question is - Why is django executing the init again. a form object was already created - the fields just need to get bound form the post data.
Second , how can I overcome this ?
**django newbie. Thanks.
Remove measure_id from init method and instead use kwrds['measure_id'] to retrieve it inside, then use them appropriately for keyword argument:
MeasureForm(request.POST, measure_id=measure_id)
MeasureForm(measure_id=measure_id)
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