How to generate HASH for Django model

Question

I am trying to generate unique HASH values for my Django models of 10 digit i have tried these methods but i am getting this error

return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: column hash_3 is not unique

Here what i have tried :

import os
import time
import hashlib
from os import path
from binascii import hexlify
from django.db import models
from django.contrib import admin
from django.core.files.storage import FileSystemStorage
#------------------------------------------------------------------------------ 

def _createHash():
    """This function generate 10 character long hash"""
    hash = hashlib.sha1()
    hash.update(str(time.time()))
    return  hash.hexdigest()[:-10]


class tags(models.Model):
    """ This is the tag model """

    seo_url1 = models.URLField()
    seo_url2 = models.URLField()
    seo_url3 = models.URLField()
    tagDescription = models.TextField()                 # Tag Description
    tag = models.CharField(max_length=200)              # Tag name
    tagSlug = models.CharField(max_length=400)          # Extra info can be added to the existing tag using this field
    updatedAt = models.DateTimeField(auto_now=True)     # Time at which tag is updated
    createdAt = models.DateTimeField(auto_now_add=True) # Time at which tag is created
    hash_1 = models.CharField(max_length=10,default=_createHash(),unique=True)
    hash_2 = models.CharField(max_length=10,default=_createHash(),unique=True)
    hash_3 = models.CharField(max_length=10,default=_createHash(),unique=True)

I have also tried this method:

def _createHash():
    """This function generate 10 character long hash"""
    return hexlify(os.urandom(5))

I have a script which inserts data into this model every time i run my script i got above mentioned error ..is there any other way of doing this..i want to store unique hash values into columns hash_1,hash_2,hash_3.

gertvdijk · Accepted Answer · 2013-05-31 09:35:33Z

15

Don't call the _createHash() function in your field, but just pass the reference to the callable in your model, e.g.

hash_1 = models.CharField(max_length=10,default=_createHash,unique=True)

As Lennart Regebro mentioned in his answer, you'll get the same value for each time you start the server in your attempt.

The Django docs say this about it:

Field.default

The default value for the field. This can be a value or a callable object. If callable it will be called every time a new object is created.

answered May 31, 2013 at 9:35

gertvdijk

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3 Comments

Vaibhav Jain Over a year ago

You are right out of curiosity but if i want to pass parameter to the method _createHash() then how do i do that.....

Vaibhav Jain Over a year ago

for instance i have a method def _generateSEOURL(pattern,StringToconcatenate): return pattern + StringToconcatenate and i want to pass seo_url1 = models.URLField(default=_generateSEOURL("discounts-in-",tag)) parameters like this ...to concatenate some string to every tag value then how do i do that...

ilovett Over a year ago

You may have to just create a wrapper function which contains the parameters you would want to pass... def _createHashForModel(): return _createHash(10) and then default=_createHashForModel

Lennart Regebro · Accepted Answer · 2013-05-31 09:24:27Z

5

_createHash() is called when you define the model, so you have the same default every time you create a new object.

You can look at creating the hash in the save() method of the model, that's probably the easiest.

answered May 31, 2013 at 9:24

Lennart Regebro

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1 Comment

Abdul Rehman Over a year ago

Hi @Lennart_Regebro, how can we use it inside the save() method?

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