In Django how can I run a custom clean function on fixture data during import and validation? - database

Question

In a ModelForm I can write a clean_<field_name> member function to automatically validate and clean up data entered by a user, but what can I do about dirty json or csv files (fixtures) during a manage.py loaddata?

Answer 1

Fixtures loaded with loaddata are assumed to contain clean data that doen't need validation (usually as an inverse operation to a prior dumpdata), so the short answer is that loaddata isn't the approach you want if you need to clean your inputs.
However, you probably can use some of the underpinnings of loaddata while implementing your custom data cleaning code--I'm sure you can easily script something using the Django serialization libs to read your existing data files them in and the save the resulting objects normally after the data has been cleaned up.

Answer 2

In case others want to do something similar, I defined a model method to do the cleaning (so it can be called from ModelForms)
MAX_ZIPCODE_DIGITS = 9
MIN_ZIPCODE_DIGITS = 5
def clean_zip_code(self, s=None):
#s = str(s or self.zip_code)
if not s: return None
s = re.sub("\D","",s)
if len(s)>self.MAX_ZIPCODE_DIGITS:
s = s[:self.MAX_ZIPCODE_DIGITS]
if len(s) in (self.MIN_ZIPCODE_DIGITS-1,self.MAX_ZIPCODE_DIGITS-1):
s = '0'+s # FIXME: deal with other intermediate lengths
if len(s)>=self.MAX_ZIPCODE_DIGITS:
s = s[:self.MIN_ZIPCODE_DIGITS]+'-'+s[self.MIN_ZIPCODE_DIGITS:]
return s
Then wrote a standalone python script to clean up my legacy json files using any clean_ methods found among the models.
import os, json
def clean_json(app = 'XYZapp', model='Entity', fields='zip_code', cleaner_prefix='clean_'):
# Set the DJANGO_SETTINGS_MODULE environment variable.
os.environ['DJANGO_SETTINGS_MODULE'] = app+".settings"
settings = __import__(app+'.settings').settings
models = __import__(app+'.models').models
fpath = os.path.join( settings.SITE_PROJECT_PATH, 'fixtures', model+'.json')
if isinstance(fields,(str,unicode)):
fields = [fields]
Ns = []
for field in fields:
try:
instance = getattr(models,model)()
except AttributeError:
print 'No model named %s could be found'%(model,)
continue
try:
cleaner = getattr(instance, cleaner_prefix+field)
except AttributeError:
print 'No cleaner method named %s.%s could be found'%(model,cleaner_prefix+field)
continue
print 'Cleaning %s using %s.%s...'%(fpath,model,cleaner.__name__)
fin = open(fpath,'r')
if fin:
l = json.load(fin)
before = len(l)
cleans = 0
for i in range(len(l)):
if 'fields' in l[i] and field in l[i]['fields']:
l[i]['fields'][field]=cleaner(l[i]['fields'][field]) # cleaner returns None to delete records
cleans += 1
fin.close()
after = len(l)
assert after>.5*before
Ns += [(before, after,cleans)]
print 'Writing %d/%d (new/old) records after %d cleanups...'%Ns[-1]
with open(fpath,'w') as fout:
fout.write(json.dumps(l,indent=2,sort_keys=True))
return Ns
if __name__ == '__main__':
clean_json()