python - Help with validation in Models and Forms -

i have few questions validation in models , forms. me out these:

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where should validation done? should in model or form? right way go have validators in form , constraints in mode?

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what difference between writing 'clean_' method in form , writing validator? i've seen people put validation checks in 'clean_' method.

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in request i'm handling, have param in url string called 'alive'. 1 or 0. correct way of defining in form? need validate number , can 1 or 0. right way?

alive = models.integerfield(null=false, max_value=1, min_value=0) 

how define default value field i.e. if parameter isn't passed, default 0 (false).

i don't have form on client side. i'm using django form validate js post request.

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in 1 of model fields need store screen resolution in format 1234x4321. should declare charfield add regular expression validation in both model , form? examples of regular expression validations helpful.

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thanks.

the validation should done on form, not model. however, if using modelforms, makes lot of sense, inherit of validation rules models (those specific database, maximum_field length, database field type, if can left blank).

the default value of field should passed constructor:

form = someform(initial={'alive' : 0}) 

although in case, appears if values can obtained 0 , one, make sense use booleanfield instead(tand in case default false).

in case of resolutions create mapping between possible resolution , arbitrary value.

resolutions = (                                                         ("1","800x600"),         ("2","1024x768"),                                      .....                         )    

and pass model:

resolutions = models.charfield(resolutions, max_length=1) 

so user gets select field corresponding options , values. on other hand, if need user insert him/herself, using 2 fields (one width, height) easier validating user input.

so can define method model:

def get_resolution(self):     return "%sx%s" % (self.width, self.height)