MongoEngine - Query Operators

Quiz

In addition to = operator to check equality, the following logical operators are defined in MongoEngine.

ne	not equal to
lt	less than
lte	less than or equal to
gt	greater than
gte	greater than or equal to
not	negate a standard check, may be used before other operators
in	value is in list
nin	value is not in list
mod	value % x == y, where x and y are two provided values
all	every item in list of values provided is in array
size	the size of the array is
exists	value for field exists

These operators must be attached to field name with double underscore __.

To use greater than (gt) operator, use the following format −

#using greater than operator
for product in products.objects(price__gt=10000):
   print ('ID:',product.ProductID, 'Name:',product.Name, 'Price:',product.price)

Output

ID: 1 Name: Laptop Price: 25000
ID: 2 Name: TV Price: 50000
ID: 5 Name: Printer Price: 12500

The in operator is like Pythons in operator. For name of product matching with names in list, the following code is used −

for product in products.objects(Name__in=['TV', 'Printer']):
print ('ID:',product.ProductID, 'Name:',product.Name, 'Price:',product.price)

Output

ID: 2 Name: TV Price: 50000
ID: 5 Name: Printer Price: 12500

You can use following operators as shortcut for regex expressions for applying filter to queries −

exact	string field exactly matches value
iexact	string field exactly matches value (case insensitive)
contains	string field contains value
icontains	string field contains value (case insensitive)
startswith	string field starts with value
istartswith	string field starts with value (case insensitive)
endswith	string field ends with value
iendswith	string field ends with value (case insensitive)
match	performs an $elemMatch so you can match an entire document within an array

For example, the following code prints product details for name containing o in name −

for product in products.objects(Name__contains='o'):
   print ('ID:',product.ProductID, 'Name:',product.Name, 'Price:',product.price)

Output

ID: 1 Name: Laptop Price: 25000
ID: 3 Name: Router Price: 2000

In another example of string query, the following code displays name ending with er−

for product in products.objects(Name__endswith='er'):
   print ('ID:',product.ProductID, 'Name:',product.Name, 'Price:',product.price)

Output

ID: 3 Name: Router Price: 2000
ID: 4 Name: Scanner Price: 5000
ID: 5 Name: Printer Price: 12500

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