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
from mongoengine import connect
from mongoengine import StringField, IntField, Document, DecimalField
connect('mydata', host='mongodb://localhost/mydata')
class Books(Document):
book_id = IntField(unique=True, required=True)
book_name = StringField(max_length=50)
book_price = DecimalField()
def _init__(self, book_id, book_name, book_price):
self.book_id = book_id
self.book_name = book_name
self.book_price = book_price
qset = Books.objects
for book in qset.filter(book_price__gt=500):
print('ID:', book.book_id, 'Name:',
book.book_name, 'Price:', book.book_price)Output
ID: 1003 Name: Machine Learning Price: 1000.00
ID: 1004 Name: Data Structure Price: 1300.00The in operator is like Python’s in operator. For name of product matching with names in list, the following code is used −
from mongoengine import connect
from mongoengine import StringField, IntField, Document, DecimalField
connect('mydata', host='mongodb://localhost/mydata')
class Books(Document):
book_id = IntField(unique=True, required=True)
book_name = StringField(max_length=50)
book_price = DecimalField()
def _init__(self, book_id, book_name, book_price):
self.book_id = book_id
self.book_name = book_name
self.book_price = book_price
qset = Books.objects
for book in qset.filter(book_price__in=range(500, 2000)):
print('ID:', book.book_id, 'Name:',
book.book_name, 'Price:', book.book_price)Output
ID: 1003 Name: Machine Learning Price: 1000.00
ID: 1004 Name: Data Structure Price: 1300.00You 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 book details for name containing ‘data’ in name −
from mongoengine import connect
from mongoengine import StringField, IntField, Document, DecimalField
connect('mydata', host='mongodb://localhost/mydata')
class Books(Document):
book_id = IntField(unique=True, required=True)
book_name = StringField(max_length=50)
book_price = DecimalField()
def _init__(self, book_id, book_name, book_price):
self.book_id = book_id
self.book_name = book_name
self.book_price = book_price
qset = Books.objects
for book in qset.filter(book_name__icontains='data'):
print('ID:', book.book_id, 'Name:',
book.book_name, 'Price:', book.book_price)Output
ID: 1004 Name: Data Structure Price: 1300.00
ID: 1005 Name: Data Structure & Algorithm Price: 1240.70
ID: 1006 Name: Data Science Price: 1600.00In another example of string query, the following code displays name ending with ‘hm’−
from mongoengine import connect
from mongoengine import StringField, IntField, Document, DecimalField
connect('mydata', host='mongodb://localhost/mydata')
class Books(Document):
book_id = IntField(unique=True, required=True)
book_name = StringField(max_length=50)
book_price = DecimalField()
def _init__(self, book_id, book_name, book_price):
self.book_id = book_id
self.book_name = book_name
self.book_price = book_price
qset = Books.objects
for book in qset.filter(book_name__endswith='hm'):
print('ID:', book.book_id, 'Name:',
book.book_name, 'Price:', book.book_price)Output
ID: 1005 Name: Data Structure & Algorithm Price: 1240.70
ID: 1007 Name: Data Analysis and Algorithm Price: 1680.00