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Autoincrementing field on object save - Django

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0

So far, I have this function:

def my_number():
 x = '0000'
 return 'MY0'.format(str(int(x) + 1).zfill(len(x)))

Which I call like this:

 number_seq = models.CharField(_("Ref."), unique=True, db_index=True,
 default=my_number, null=True)

It works, but when I try to save a new document, it just creates a new MY0001, and it should be incrementing, like MY0002, MY0003 and so forth.

What might be the reason for that?

django python-3.x

share|improve this question

asked Mar 26 at 13:34

NeoVeNeoVe

2,07666 gold badges3333 silver badges8181 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Well, you are using a variable from the local scope you are setting to 0. Why would you expect it to change?
  
  – Alvaro
  Mar 26 at 13:37
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I tried like = x = 1 return 'MY0'.format(str(int(x) + 1).zfill(4)) But it's stuck on MY0002 now, I'm a bit confused
  
  – NeoVe
  Mar 26 at 13:47
  
  

  
  
  
  

add a comment | 

0

So far, I have this function:

def my_number():
 x = '0000'
 return 'MY0'.format(str(int(x) + 1).zfill(len(x)))

Which I call like this:

 number_seq = models.CharField(_("Ref."), unique=True, db_index=True,
 default=my_number, null=True)

It works, but when I try to save a new document, it just creates a new MY0001, and it should be incrementing, like MY0002, MY0003 and so forth.

What might be the reason for that?

django python-3.x

share|improve this question

asked Mar 26 at 13:34

NeoVeNeoVe

2,07666 gold badges3333 silver badges8181 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Well, you are using a variable from the local scope you are setting to 0. Why would you expect it to change?
  
  – Alvaro
  Mar 26 at 13:37
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I tried like = x = 1 return 'MY0'.format(str(int(x) + 1).zfill(4)) But it's stuck on MY0002 now, I'm a bit confused
  
  – NeoVe
  Mar 26 at 13:47
  
  

  
  
  
  

add a comment | 

So far, I have this function:

def my_number():
 x = '0000'
 return 'MY0'.format(str(int(x) + 1).zfill(len(x)))

Which I call like this:

 number_seq = models.CharField(_("Ref."), unique=True, db_index=True,
 default=my_number, null=True)

It works, but when I try to save a new document, it just creates a new MY0001, and it should be incrementing, like MY0002, MY0003 and so forth.

What might be the reason for that?

django python-3.x

share|improve this question

asked Mar 26 at 13:34

NeoVeNeoVe

2,07666 gold badges3333 silver badges8181 bronze badges

def my_number():
 x = '0000'
 return 'MY0'.format(str(int(x) + 1).zfill(len(x)))

 number_seq = models.CharField(_("Ref."), unique=True, db_index=True,
 default=my_number, null=True)

share|improve this question

asked Mar 26 at 13:34

NeoVeNeoVe

2,07666 gold badges3333 silver badges8181 bronze badges

share|improve this question

asked Mar 26 at 13:34

NeoVeNeoVe

2,07666 gold badges3333 silver badges8181 bronze badges

asked Mar 26 at 13:34

NeoVeNeoVe

2,07666 gold badges3333 silver badges8181 bronze badges

asked Mar 26 at 13:34

NeoVeNeoVe

2,07666 gold badges3333 silver badges8181 bronze badges

1 Answer
1

active

oldest

votes

2

Rather than taking your approach, I think you should declare a AutoField as primary key, and maybe have a property method named number_seq to get the value for reference. For example:

class SomeModel(models.Model):
 your_pk = models.AutoField(primary_key=True)

 @property
 def number_seq(self):
 return 'MY0'.format(str(self.your_pk).zfill(4))

But you can't run query against it directly, like SomeModel.objects.filter(number_seq="MY001") will not work. But you can do the following to get the needed objects. For example:

value = "MY001"
SomeModel.objects.get(pk=int(value[2:]))

share|improve this answer

answered Mar 26 at 13:50

ruddraruddra

21k55 gold badges3131 silver badges5353 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Hi, thank you very much, sounds good, but most of my child models will need to have this property now, I don't know if it will be safe with this approach
  
  – NeoVe
  Mar 26 at 14:01
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Sorry i didn't get what you meant with what kind of safety you are referring to
  
  – ruddra
  Mar 26 at 14:13
  
  

  
  
  
  

add a comment | 

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2

Rather than taking your approach, I think you should declare a AutoField as primary key, and maybe have a property method named number_seq to get the value for reference. For example:

class SomeModel(models.Model):
 your_pk = models.AutoField(primary_key=True)

 @property
 def number_seq(self):
 return 'MY0'.format(str(self.your_pk).zfill(4))

But you can't run query against it directly, like SomeModel.objects.filter(number_seq="MY001") will not work. But you can do the following to get the needed objects. For example:

value = "MY001"
SomeModel.objects.get(pk=int(value[2:]))

share|improve this answer

answered Mar 26 at 13:50

ruddraruddra

21k55 gold badges3131 silver badges5353 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Hi, thank you very much, sounds good, but most of my child models will need to have this property now, I don't know if it will be safe with this approach
  
  – NeoVe
  Mar 26 at 14:01
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Sorry i didn't get what you meant with what kind of safety you are referring to
  
  – ruddra
  Mar 26 at 14:13
  
  

  
  
  
  

add a comment | 

2

Rather than taking your approach, I think you should declare a AutoField as primary key, and maybe have a property method named number_seq to get the value for reference. For example:

class SomeModel(models.Model):
 your_pk = models.AutoField(primary_key=True)

 @property
 def number_seq(self):
 return 'MY0'.format(str(self.your_pk).zfill(4))

But you can't run query against it directly, like SomeModel.objects.filter(number_seq="MY001") will not work. But you can do the following to get the needed objects. For example:

value = "MY001"
SomeModel.objects.get(pk=int(value[2:]))

share|improve this answer

answered Mar 26 at 13:50

ruddraruddra

21k55 gold badges3131 silver badges5353 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Hi, thank you very much, sounds good, but most of my child models will need to have this property now, I don't know if it will be safe with this approach
  
  – NeoVe
  Mar 26 at 14:01
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Sorry i didn't get what you meant with what kind of safety you are referring to
  
  – ruddra
  Mar 26 at 14:13
  
  

  
  
  
  

add a comment | 

Rather than taking your approach, I think you should declare a AutoField as primary key, and maybe have a property method named number_seq to get the value for reference. For example:

class SomeModel(models.Model):
 your_pk = models.AutoField(primary_key=True)

 @property
 def number_seq(self):
 return 'MY0'.format(str(self.your_pk).zfill(4))

But you can't run query against it directly, like SomeModel.objects.filter(number_seq="MY001") will not work. But you can do the following to get the needed objects. For example:

value = "MY001"
SomeModel.objects.get(pk=int(value[2:]))

share|improve this answer

answered Mar 26 at 13:50

ruddraruddra

21k55 gold badges3131 silver badges5353 bronze badges

class SomeModel(models.Model):
 your_pk = models.AutoField(primary_key=True)

 @property
 def number_seq(self):
 return 'MY0'.format(str(self.your_pk).zfill(4))

value = "MY001"
SomeModel.objects.get(pk=int(value[2:]))

share|improve this answer

answered Mar 26 at 13:50

ruddraruddra

21k55 gold badges3131 silver badges5353 bronze badges

answered Mar 26 at 13:50

ruddraruddra

21k55 gold badges3131 silver badges5353 bronze badges

answered Mar 26 at 13:50

ruddraruddra

21k55 gold badges3131 silver badges5353 bronze badges