I'm trying to create a model where one of the fields should be an Age field, but that instead of being a simple number (IntegerField), I needed to be a Choice of several available age ranges (5-8, 8-12, 12-18, 18-99, 5-99). I'm looking at the documentation of Choices, but I'm not even sure I can use directly an IntegerRangeField in this, so I ended up with something like this:
class Person(models.Model):
FIRST_RANGE = IntegerRangeField(blank=True, validators=[MinValueValidator(5), MaxValueValidator(8)])
SECOND_RANGE = IntegerRangeField(blank=True, validators=[MinValueValidator(8), MaxValueValidator(12)])
THIRD_RANGE = IntegerRangeField(blank=True, validators=[MinValueValidator(12), MaxValueValidator(18)])
FOURTH_RANGE = IntegerRangeField(blank=True, validators=[MinValueValidator(18), MaxValueValidator(99)])
FIFTH_RANGE = IntegerRangeField(blank=True, validators=[MinValueValidator(18), MaxValueValidator(99)])
AGE_CHOICES = (
(FIRST_RANGE, '5-8'),
(SECOND_RANGE, '8-12'),
(THIRD_RANGE, '12-18'),
(FOURTH_RANGE, '18-99'),
(FIFTH_RANGE, '5-99'),
)
age = models.IntegerRangeField(blank=True, choices=AGE_CHOICES)
Is this the correct approach for this? This looks a bit awkward to me, I'm considering just using Char instead, although I'd like to stick to a have a Range on this field at the end...
Thanks!
From the documentation of Range Fields in django:
All of the range fields translate to psycopg2 Range objects in python, but also accept tuples as input if no bounds information is necessary. The default is lower bound included, upper bound excluded.
It seems you can use tuples to create the choices.
FIRST_RANGE = (5, 8) # here 5 is included and 8 is excluded
# and similarly create the other ranges and then use in AGE_CHOICES
Alternatively, you can create the Range objects.
from psycopg2.extras import Range
FIRST_RANGE = Range(lower=5, upper=8, bounds='[)')
# bounds: one of the literal strings (), [), (], [], representing whether the lower or upper bounds are included
Related
I had a huge registration table with 112 fields. For a particular search I want to compare 17 fields & assign colors to variable say 'clrSelected'.
My code is :
reg = Regisration.objects.filter('some condition').order_by("name")
for r in reg:
if r.name=='abc': clrSelected='#fff'
if r.type=='1': clrSelected='#000'
if r.appl=='10': clrSelected='#c1ff51'
if r.code=='': clrSelected='#60c5f7'
if r.qlty=='first': clrSelected='#f99334'
...
...
there will be only one if condition, which need to be colored. Which means the field(from the dictionary) to be compared will change based on the user selection.
I want to access the field name from a dictionary like this
flds = {'1':'name', '2':'type', '3':'appl', '4':'code', '5':'qlty',...}
And use it something like this
if r.flds['1']=='abc': clrSelected='#fff'
How could i use the fields as above. I am using django 1.4 & python 2.7
Just to answer the question, you could use getattr:
if getattr(r, flds['1']) == 'abc': clrSelected = '#fff'
However, I am pretty sure that you could go with a different kind of implementation in this case which doesn't require using a dict like this.
I would suggest using a three tuple list: (fieldName, value, color)
some_list = [('name', 'abc', '#fff'), ('type', '1', '#000'), ...]
And, then use this list to determine the color:
for fieldName, value, color in some_list:
if getattr(r, fieldName) == value:
clrSelected = color
Looking at your implementation, it seems the color will be based on the last if condition which matches. If that is the case, you could create some_list in reverse order and break on the first matching condition.
I am trying to populate a list in Python3 with 3 random items being read from a file using REGEX, however i keep getting duplicate items in the list.
Here is an example.
import re
import random as rn
data = '/root/Desktop/Selenium[FILTERED].log'
with open(data, 'r') as inFile:
index = inFile.read()
URLS = re.findall(r'https://www\.\w{1,10}\.com/view\?i=\w{1,20}', index)
list_0 = []
for i in range(3):
list_0.append(URLS[rn.randint(1, 30)])
inFile.close()
for i in range(len(list_0)):
print(list_0[i])
What would be the cleanest way to prevent duplicate items being appended to the list?
(EDIT)
This is the code that i think has done the job quite well.
def random_sample(data):
r_e = ['https://www\.\w{1,10}\.com/view\?i=\w{1,20}', '..']
with open(data, 'r') as inFile:
urls = re.findall(r'%s' % r_e[0], inFile.read())
x = list(set(urls))
inFile.close()
return x
data = '/root/Desktop/[TEMP].log'
sample = random_sample(data)
for i in range(3):
print(sample[i])
Unordered collection with no duplicate entries.
Use the builtin random.sample.
random.sample(population, k)
Return a k length list of unique elements chosen from the population sequence or set.
Used for random sampling without replacement.
Addendum
After seeing your edit, it looks like you've made things much harder than they have to be. I've wired a list of URLS in the following, but the source doesn't matter. Selecting the (guaranteed unique) subset is essentially a one-liner with random.sample:
import random
# the following two lines are easily replaced
URLS = ['url1', 'url2', 'url3', 'url4', 'url5', 'url6', 'url7', 'url8']
SUBSET_SIZE = 3
# the following one-liner yields the randomized subset as a list
urlList = [URLS[i] for i in random.sample(range(len(URLS)), SUBSET_SIZE)]
print(urlList) # produces, e.g., => ['url7', 'url3', 'url4']
Note that by using len(URLS) and SUBSET_SIZE, the one-liner that does the work is not hardwired to the size of the set nor the desired subset size.
Addendum 2
If the original list of inputs contains duplicate values, the following slight modification will fix things for you:
URLS = list(set(URLS)) # this converts to a set for uniqueness, then back for indexing
urlList = [URLS[i] for i in random.sample(range(len(URLS)), SUBSET_SIZE)]
Or even better, because it doesn't need two conversions:
URLS = set(URLS)
urlList = [u for u in random.sample(URLS, SUBSET_SIZE)]
seen = set(list_0)
randValue = URLS[rn.randint(1, 30)]
# [...]
if randValue not in seen:
seen.add(randValue)
list_0.append(randValue)
Now you just need to check list_0 size is equal to 3 to stop the loop.
A lot of websites will display:
"1.8K pages" instead of "1,830 pages"
or
"43.2M pages" instead of "43,200,123 pages"
Is there a way to do this in Django?
For example, the following code will generate the quantified amount of objects in the queryset (i.e. 3,123):
Books.objects.all().count()
Is there a way to add a custom count filter to return "3.1K pages" instead of "3,123 pages?
Thank you in advance!
First off, I wouldn't do anything that alters the way the ORM portion of Django works. There are two places this could be done, if you are only planning on using it in one place - do it on the frontend. With that said, there are many ways to achieve this result. Just to spout off a few ideas, you could write a property on your model that calls count then converts that to something a little more human readable for the back end. If you want to do it on the frontend you might want to find a JavaScript lib that could do the conversion.
I will edit this later from my computer and add an example of the property.
Edit: To answer your comment, the easier one to implement depends on your skills in python vs in JavaScript. I prefer python so I would probably do it in there somewhere on the model.
Edit2: I have wrote an example to show you how I would do a classmethod on a base model or on the model that you need these numbers on. I found a python package called humanize and I took its function that converts these to readable and modified it a bit to allow for thousands and took out some of the super large number conversion.
def readable_number(value, short=False):
# Modified from the package `humanize` on pypy.
powers = [10 ** x for x in (3, 6, 9, 12, 15, 18)]
human_powers = ('thousand', 'million', 'billion', 'trillion', 'quadrillion')
human_powers_short = ('K', 'M', 'B', 'T', 'QD')
try:
value = int(value)
except (TypeError, ValueError):
return value
if value < powers[0]:
return str(value)
for ordinal, power in enumerate(powers[1:], 1):
if value < power:
chopped = value / float(powers[ordinal - 1])
chopped = format(chopped, '.1f')
if not short:
return '{} {}'.format(chopped, human_powers[ordinal - 1])
return '{}{}'.format(chopped, human_powers_short[ordinal - 1])
class MyModel(models.Model):
#classmethod
def readable_count(cls, short=True):
count = cls.objects.all().count()
return readable_number(count, short=short)
print(readable_number(62220, True)) # Returns '62.2K'
print(readable_number(6555500)) # Returns '6.6 million'
I would stick that readable_number in some sort of utils and just import it in your models file. Once you have that, you can just stick that string wherever you would like on your frontend.
You would use MyModel.readable_count() to get that value. If you want it under MyModel.objects.readable_count() you will need to make a custom object manager for your model, but that is a bit more advanced.
One field in my model is a charField with the format substring1-substring2-substring3-substring4 and it can have this range of values:
"1-1-2-1"
"1-1-2-2"
"1-1-2-3"
"1-1-2-4"
"2-2-2-6"
"2-2-2-7"
"2-2-2-9"
"3-1-1-10"
"10-1-1-11"
"11-1-1-12"
"11-1-1-13"
For example I need to count the single number of occurrences for substring1.
In this case there are 5 unique occurrences (1,2,3,10,11).
"1-X-X-X"
"2-X-X-X"
"3-X-X-X"
"10-X-X-X"
"11-X-X-XX"
Sincerely I don't know where I can start from. I read the doc https://docs.djangoproject.com/en/1.5/ref/models/querysets/ but I didn't find a specific clue.
Thanks in advance.
results = MyModel.objects.all()
pos_id = 0
values_for_pos_id = [res.field_to_check.split('-')[pos_id] for res in results]
values_for_pos_id = set(values_for_pos_id)
How does this work:
first you fetch all your objects (results)
pos_id is your substring index (you have 4 substring, so it's in range 0 to 3)
you split each field_to_check (aka: where you store the substring combinations) on - (your separator) and fetch the correct substring for that object
you convert the list to a set (to have all the unique values)
Then a simple len(values_for_pos_id) will do the trick for you
NB: If you don't have pos_id or can't set it anywhere, you just need to loop like this:
for pos_id in range(4):
values_for_pos_id = set([res.field_to_check.split('-')[pos_id] for res in results])
# process your set results now
print len(values_for_pos_id)
Try something like this...
# Assumes your model name is NumberStrings and attribute numbers stores the string.
search_string = "1-1-2-1"
matched_number_strings = NumberStrings.objects.filter(numbers__contains=search_string)
num_of_occurrences = len(matches_found)
matched_ids = [match.id for match in matched_number_strings]
You could loop through these items (I guess they're strings), and add the value of each substring_n to a Set_n.
Since set values are unique, you would have a set, called Set_1, for example, that contains 1,2,3,10,11.
Make sense?
I'm in a situation where I must output a quite large list of objects by a CharField used to store street addresses.
My problem is, that obviously the data is ordered by ASCII codes since it's a Charfield, with the predictable results .. it sort the numbers like this;
1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 2, 20, 21....
Now the obvious step would be to change the Charfield the proper field type (IntegerField let's say), however it cannot work since some address might have apartments .. like "128A".
I really don't know how I can order this properly ..
If you're sure there are only integers in the field, you could get the database to cast it as an integer via the extra method, and order by that:
MyModel.objects.extra(
select={'myinteger': 'CAST(mycharfield AS INTEGER)'}
).order_by('myinteger')
Django is trying to deprecate the extra() method, but has introduced Cast() in v1.10. In sqlite (at least), CAST can take a value such as 10a and will cast it to the integer 10, so you can do:
from django.db.models import IntegerField
from django.db.models.functions import Cast
MyModel.objects.annotate(
my_integer_field=Cast('my_char_field', IntegerField())
).order_by('my_integer_field', 'my_char_field')
which will return objects sorted by the street number first numerically, then alphabetically, e.g. ...14, 15a, 15b, 16, 16a, 17...
If you're using PostgreSQL (not sure about MySQL) you can safely use following code on char/text fields and avoid cast errors:
MyModel.objects.extra(
select={'myinteger': "CAST(substring(charfield FROM '^[0-9]+') AS INTEGER)"}
).order_by('myinteger')
Great tip! It works for me! :) That's my code:
revisioned_objects = revisioned_objects.extra(select={'casted_object_id': 'CAST(object_id AS INTEGER)'}).extra(order_by = ['casted_object_id'])
I know that I’m late on this, but since it’s strongly related to the question, and that I had a hard time finding this:
You have to know that you can directly put the Cast in the ordering option of your model.
from django.db import models
from django.db.models.functions import Cast
class Address(models.Model):
street_number = models.CharField()
class Meta:
ordering = [
Cast("street_number", output_field=models.IntegerField()),
]
From the doc about ordering:
You can also use query expressions.
And from the doc about database functions:
Functions are also expressions, so they can be used and combined with other expressions like aggregate functions.
The problem you're up against is quite similar to how filenames get ordered when sorting by filename. There, you want "2 Foo.mp3" to appear before "12 Foo.mp3".
A common approach is to "normalize" numbers to expanding to a fixed number of digits, and then sorting based on the normalized form. That is, for purposes of sorting, "2 Foo.mp3" might expand to "0000000002 Foo.mp3".
Django won't help you here directly. You can either add a field to store the "normalized" address, and have the database order_by that, or you can do a custom sort in your view (or in a helper that your view uses) on address records before handing the list of records to a template.
In my case i have a CharField with a name field, which has mixed (int+string) values, for example. "a1", "f65", "P", "55" e.t.c ..
Solved the issue by using the sql cast (tested with postgres & mysql),
first, I try to sort by the casted integer value, and then by the original value of the name field.
parking_slots = ParkingSlot.objects.all().extra(
select={'num_from_name': 'CAST(name AS INTEGER)'}
).order_by('num_from_name', 'name')
This way, in any case, the correct sorting works for me.
In case you need to sort version numbers consisting of multiple numbers separated by a dot (e.g. 1.9.0, 1.10.0), here is a postgres-only solution:
class VersionRecordManager(models.Manager):
def get_queryset(self):
return super().get_queryset().extra(
select={
'natural_version': "string_to_array(version, '.')::int[]",
},
)
def available_versions(self):
return self.filter(available=True).order_by('-natural_version')
def last_stable(self):
return self.available_versions().filter(stable=True).first()
class VersionRecord(models.Model):
objects = VersionRecordManager()
version = models.CharField(max_length=64, db_index=True)
available = models.BooleanField(default=False, db_index=True)
stable = models.BooleanField(default=False, db_index=True)
In case you want to allow non-numeric characters (e.g. 0.9.0 beta, 2.0.0 stable):
def get_queryset(self):
return super().get_queryset().extra(
select={
'natural_version':
"string_to_array( "
" regexp_replace( " # Remove everything except digits
" version, '[^\d\.]+', '', 'g' " # and dots, then split string into
" ), '.' " # an array of integers.
")::int[] "
}
)
I was looking for a way to sort the numeric chars in a CharField and my search led me here. The name fields in my objects are CC Licenses, e.g., 'CC BY-NC 4.0'.
Since extra() is going to be deprecated, I was able to do it this way:
MyObject.objects.all()
.annotate(sorting_int=Cast(Func(F('name'), Value('\D'), Value(''), Value('g'), function='regexp_replace'), IntegerField()))
.order_by('-sorting_int')
Thus, MyObject with name='CC BY-NC 4.0' now has sorting_int=40.
All the answeres in this thread did not work for me because they are assuming numerical text. I found a solution that will work for a subset of cases. Consider this model
Class Block(models.Model):
title = models.CharField()
say I have fields that sometimes have leading characters and trailing numerical characters If i try and order normally
>>> Block.objects.all().order_by('title')
<QuerySet [<Block: 1>, <Block: 10>, <Block: 15>, <Block: 2>, <Block: N1>, <Block: N12>, <Block: N4>]>
As expected, it's correct alphabetically, but makes no sense for us humans. The trick that I did for this particular use case is to replace any text i find with the number 9999 and then cast the value to an integer and order by it.
for most cases that have leading characters this will get the desired result. see below
from django.db.models.expressions import RawSQL
>>> Block.objects.all()\
.annotate(my_faux_integer=RawSQL("CAST(regexp_replace(title, '[A-Z]+', '9999', 'g') AS INTEGER)", ''))\
.order_by('my_faux_integer', 'title')
<QuerySet [<Block: 1>, <Block: 2>, <Block: 10>, <Block: 15>, <Block: N1>, <Block: N4>, <Block: N12>]>