Future Of Technology - Django

Introduction:
     This section will teach you to How to create not equal queryset filtering.

Method:

from django.db.models import Q
    Models.objects.exclude(MyField='foo')
    Models.objects.filter(~Q(MyField='foo'))

Introduction:
     This section will teach you to How to create complex query/filter using django Q objects.

Method:

from django.db.models import Q
    q_object = Q()
    q_object.add(Q(MyField__icontains='foo'), Q.OR) # OR'ing
    q_object.add(Q(MyField__icontains='foo'), Q.AND) # AND'ing
    q_object.add(Q(**{'MyField': 'foo'}), Q.AND) # QueryDict

Introduction:
     This section will teach you to How to create dynamic menu in templates. Here we used ``context processors``

Method:

• create a file say `context_processors.py` inside your application folder.
• File looks like

from models import GameCategory
def Category(request):
    category_list=list(GameCategory.objects.all())
    return {'category_list':category_list}

• In Settings.py

TEMPLATE_CONTEXT_PROCESSORS = (
    'MyProject.MyApplication.context_processors.Category', # path to above-said file(context_processors.py)
)

• Now you can able to get the ``category_list`` in your Base.html
  

Introduction
Easy way to Import & Export as CSV file in postgreSQL using psql copy command.

Query:

Import
COPY tablename From '/absolute _path_to_file/filename.csv' DELIMITERS '|' WITH NULL AS '';

Export
COPY tablename To '/absolute _path_to_file/filename.csv' DELIMITERS '|' WITH NULL AS '';

• User should be superuser i.e postgres.
• Path should be absolute and have full permission (chmod 777).
• Should be in local-machine where postgreSQL installed.
• While importing data from csv to DB, the field and data order should be same. (Say, If we have table with fields as ID & Name, then data in csv file should be 1 & Jayapal )
  

Introduction:

• Script use to get the pincode from a address. I used regulatr expression to find it. At first, we will check check pincode end of address. If we didn't get, then check between address. Here I assumed pincode starts with 7 and len should be 6 (ex 700002)

def getPin(myStr):
pin=re.search(r"7(\d{0,5})$",myStr)# check for pincode end of string
if not pin:
pin=re.search(r"7(\d{0,5})[ ]",myStr) # check for pincode in between string
return pin

Introduction:

• Simply ignoring NULL characters while reading CSV file.

def nonull(stream):
    for line in stream:
        yield line.replace('\x00', '')

reader = csv.reader(nonull(open(os.getcwd()+"/test.csv")), dialect='excel', delimiter='|')

Introduction:

• Check whether string is in printable format. This would be useful when we parse unformatted csv file.

def check(myStr):
    return filter(lambda x: x in string.printable, myStr)