Question

I have a Django app that allows the user to create variables and name them

class Product(models.Model):
    name = models.CharField(max_length=40, unique=True)
    int1_name = models.CharField(max_length=60, blank=True, null=True)
    int1_default = models.IntegerField(blank=True, null=True)
    int2_name = models.CharField(max_length=60, blank=True, null=True)
    int2_default = models.IntegerField(blank=True, null=True)
    float1_name = models.CharField(max_length=60, blank=True, null=True)
    float1_default = models.FloatField(blank=True, null=True)
    float2_name = models.CharField(max_length=60, blank=True, null=True)
    float2_default = models.FloatField(blank=True, null=True)
    string1_name = models.CharField(max_length=60, blank=True, null=True)
    string1_default = models.CharField(max_length=60, blank=True, null=True)
    string2_name = models.CharField(max_length=60, blank=True, null=True)
    string2_default = models.CharField(max_length=60, blank=True, null=True)

And then they are stored

class ItemData(models.Model):
    created = models.DateTimeField(default=datetime.now)
    item = models.ForeignKey(Item, editable=False)
    int1_val = models.IntegerField(blank=True, null=True)
    int2_val = models.IntegerField(blank=True, null=True)
    float1_val = models.DecimalField(blank=True, null=True, max_digits=12, decimal_places=2)
    float2_val = models.DecimalField(blank=True, null=True, max_digits=12, decimal_places=2)
    string1_val = models.CharField(max_length=60, blank=True, null=True)
    string2_val = models.CharField(max_length=60, blank=True, null=True)

And at the moment when I present the user with a form (that they have created) to fill in I do the following to lable up the fields with the names that user has given there variables

class ItemDataForm(ModelForm):

    # Only renames the fields based on whether the product has a name for the field
    def __init__(self,product,*args,**kwargs):
        super(ItemDataForm, self).__init__(*args, **kwargs)
        # delete all the fields that will be automatically filled in when saving
        del self.fields['created']
        # if the values is set in the product
        if product.int1_name:
            self.fields['int1_val'].label = product.int1_name
            self.fields['int1_val'].value = product.int1_default
        else:
            del self.fields['int1_val']
        if product.int2_name:
            self.fields['int2_val'].label = product.int2_name
            self.fields['int2_val'].value = product.int2_default
        else:
            del self.fields['int2_val']
        if product.float1_name:
            self.fields['float1_val'].label = product.float1_name
            self.fields['float1_val'].value = product.float1_default
        else:
            del self.fields['float1_val']
        if product.float2_name:
            self.fields['float2_val'].label = product.float2_name
            self.fields['float2_val'].value = product.float2_default
        else:
            del self.fields['float2_val']
        if product.string1_name:
            self.fields['string1_val'].label = product.string1_name
            self.fields['string1_val'].value = product.string1_default
        else:
            del self.fields['string1_val']
        if product.string2_name:
            self.fields['string2_val'].label = product.string2_name
            self.fields['string2_val'].value = product.string2_default
        else:
            del self.fields['string2_val']

Is there any way I could do this a bit more pythonicaly like have a list is settings.py and loop over it:

USER_SETTABLE_VARIABLES = ['int1','int2','float1','float2','string1','string2']

The same applies to the way I make sure that the data entered is unique before saving:

def is_unique(self,latestSI):
    if (self.cleaned_data['int1_val'] == latestSI.int1_val and
        self.cleaned_data['int2_val'] == latestSI.int2_val and
        self.cleaned_data['float1_val'] == latestSI.float1_val and
        self.cleaned_data['float2_val'] == latestSI.float2_val and
        self.cleaned_data['string1_val'] == latestSI.string1_val and
        self.cleaned_data['string2_val'] == latestSI.string2_val):
        return False
    else:
        return True

I only ask because when I want to add to the model I don’t want to be editing all these functions.

Answer 1

Don’t use exec for this! getattr is perfectly adequate, much safer, and readable too.

class ItemDataForm(ModelForm):
    def __init__(self,product,*args,**kwargs):
        super(ItemDataForm, self).__init__(*args, **kwargs)
        del self.fields['created']
        fields = 'int1', 'int2', 'float1', 'float2', 'string1', 'string2'
        for field in fields:
            val = getattr(product, field + '_name')
            fval = field + '_val'
            if val:
                self.fields[fval].label = val
                self.fields[fval].value = getattr(product, field + '_default')
            else:
                del self.fields[fval]