Python MongoDB Tutorial – Using limit() with PyMongo

Last updated 2 weeks ago | 37 views 75     5

Tags:- Python MongoDB

When working with large datasets in MongoDB, retrieving all documents is often unnecessary and inefficient. Fortunately, MongoDB provides a simple method to limit the number of documents returned in a query.

In this tutorial, you'll learn how to use the limit() function with PyMongo in Python to control your query results efficiently.


Table of Contents

  1. What is limit() in MongoDB?

  2. Why Use limit()?

  3. Prerequisites

  4. Installing PyMongo

  5. Connecting to MongoDB

  6. Inserting Sample Documents

  7. Using limit() with find()

  8. Combining limit() with sort()

  9. Full Working Example

  10. Tips and Common Pitfalls


1. What is limit() in MongoDB?

The limit() method is used to restrict the number of documents returned by a query. For example, if you want only the first 5 records, use:

collection.find().limit(5)

❓ 2. Why Use limit()?

  •  Reduce data transfer for faster performance

  •  Improve efficiency in paginated APIs

  • Useful for previewing data

  • Ideal in testing or sampling records


⚙️ 3. Prerequisites

  • Python 3.x installed

  • MongoDB running locally or on MongoDB Atlas

  • Basic knowledge of MongoDB and Python


4. Installing PyMongo

Install the PyMongo package using pip:

pip install pymongo

5. Connecting to MongoDB

Connect to a local MongoDB database:

import pymongo

client = pymongo.MongoClient("mongodb://localhost:27017/")
db = client["mydatabase"]
collection = db["students"]

6. Inserting Sample Documents

Insert multiple records into the students collection:

collection.insert_many([
    {"name": "Alice", "score": 87},
    {"name": "Bob", "score": 91},
    {"name": "Charlie", "score": 78},
    {"name": "David", "score": 85},
    {"name": "Eve", "score": 92},
    {"name": "Frank", "score": 74}
])

7. Using limit() with find()

Retrieve only the first 3 documents:

results = collection.find().limit(3)

for student in results:
    print(student)

Output will show only three student documents.


8. Combining limit() with sort()

You can combine limit() with sort() to get top or bottom records:

# Top 2 scorers
results = collection.find().sort("score", -1).limit(2)

for student in results:
    print(student)

This sorts by score in descending order and returns the top 2 scorers.


9. Full Working Example

import pymongo

# Connect to MongoDB
client = pymongo.MongoClient("mongodb://localhost:27017/")
db = client["mydatabase"]
collection = db["students"]

# Insert sample data
collection.insert_many([
    {"name": "Alice", "score": 87},
    {"name": "Bob", "score": 91},
    {"name": "Charlie", "score": 78},
    {"name": "David", "score": 85},
    {"name": "Eve", "score": 92},
    {"name": "Frank", "score": 74}
])

# Limit results to 3
print("Limit to 3 students:")
for student in collection.find().limit(3):
    print(student)

# Top 2 scorers
print("\nTop 2 scorers:")
for student in collection.find().sort("score", -1).limit(2):
    print(student)

10. Tips and Common Pitfalls

Tip / Pitfall Description
✅ Always use limit() in UI views Avoid over-fetching records
limit() doesn’t guarantee order Use sort() with limit()
✅ Use in pagination logic Combine with skip() for pagination
 Avoid hardcoded limits in logic Make limits configurable
✅ Use count_documents() to check totals Useful for paginated API responses

✅ Conclusion

The limit() method in PyMongo is a simple yet powerful way to control data output from MongoDB queries. Whether you're building paginated results, analyzing top records, or just testing your collections, limit() helps you avoid unnecessary load and keep your application efficient.

Keep it fast. Keep it clean. Use limit().

 

Tips and Tricks


What is pass in Python?

Python | Pass Statement

The pass statement is used as a placeholder for future code. It represents a null operation in Python. It is generally used for the purpose of filling up empty blocks of code which may execute during runtime but has yet to be written.

 

def myfunction():
    pass

 


How can you generate random numbers?

Python | Generate random numbers

Python provides a module called random using which we can generate random numbers. e.g: print(random.random())

 

 

We have to import a random module and call the random() method as shown below:

 import random

 print(random.random())

The random() method generates float values lying between 0 and 1 randomly.


To generate customized random numbers between specified ranges, we can use the randrange() method
Syntax: randrange(beginning, end, step)
 

import random

print(random.randrange(5,100,2))

 


What is lambda in Python?

Python | Lambda function

A lambda function is a small anonymous function. This function can have any number of parameters but, can have just one statement.
 

 

Syntex: 
lambda arguments : expression
 

a = lambda x,y : x+y

print(a(5, 6))

It also provides a nice way to write closures. With that power, you can do things like this.

def adder(x):
    return lambda y: x + y

add5 = adder(5)

add5(1)    #6

As you can see from the snippet of Python, the function adder takes in an argument x and returns an anonymous function, or lambda, that takes another argument y. That anonymous function allows you to create functions from functions. This is a simple example, but it should convey the power lambdas and closures have.
 


What is swapcase() function in the Python?

Python | swapcase() Function

It is a string's function that converts all uppercase characters into lowercase and vice versa. It automatically ignores all the non-alphabetic characters.
 

string = "IT IS IN LOWERCASE."  

print(string.swapcase())  

 


How to remove whitespaces from a string in Python?

Python | strip() Function | Remove whitespaces from a string 

To remove the whitespaces and trailing spaces from the string, Python provides a strip([str]) built-in function. This function returns a copy of the string after removing whitespaces if present. Otherwise returns the original string.
 

string = "  Python " 
 
print(string.strip())  

 


What is the usage of enumerate() function in Python?

Python | enumerate() Function

The enumerate() function is used to iterate through the sequence and retrieve the index position and its corresponding value at the same time.
 

lst = ["A","B","C"] 
 
print (list(enumerate(lst)))

#[(0, 'A'), (1, 'B'), (2, 'C')]

 


Can you explain the filter(), map(), and reduce() functions?

Python | filter(), map(), and reduce() Functions

  • filter()  function accepts two arguments, a function and an iterable, where each element of the iterable is filtered through the function to test if the item is accepted or not.
    >>> set(filter(lambda x:x>4, range(7)))
    
    # {5, 6}
    
    

     

  • map() function calls the specified function for each item of an iterable and returns a list of result

    >>> set(map(lambda x:x**3, range(7)))
    
    # {0, 1, 64, 8, 216, 27, 125}

     

  • reduce() function reduces a sequence pair-wise, repeatedly until we arrive at a single value..
     

    >>> reduce(lambda x,y:y-x, [1,2,3,4,5])
    
    # 3
    

    Let’s understand this:

    2-1=1
    3-1=2
    4-2=2
    5-2=3

    Hence, 3.

 


What is a namedtuple?

Python | namedtuple

A namedtuple will let us access a tuple’s elements using a name/label. We use the function namedtuple() for this, and import it from collections.

>>> from collections import namedtuple

#format
>>> result=namedtuple('result','Physics Chemistry Maths') 

#declaring the tuple
>>> Chris=result(Physics=86,Chemistry=92,Maths=80) 

>>> Chris.Chemistry
# 92

 


Write a code to add the values of same keys in two different dictionaries and return a new dictionary.

We can use the Counter method from the collections module

from collections import Counter

dict1 = {'a': 5, 'b': 3, 'c': 2}
dict2 = {'a': 2, 'b': 4, 'c': 3}

new_dict = Counter(dict1) + Counter(dict2)


print(new_dict)
# Print: Counter({'a': 7, 'b': 7, 'c': 5})


 


Python In-place swapping of two numbers

 Python | In-place swapping of two numbers

>>> a, b = 10, 20
>>> print(a, b)
10 20

>>> a, b = b, a
>>> print(a, b)
20 10

 


Reversing a String in Python

Python | Reversing a String

>>> x = 'PythonWorld'
>>> print(x[: : -1])
dlroWnohtyP

 


Python join all items of a list to convert into a single string

Python | Join all items of a list to convert into a single string

>>> x = ["Python", "Online", "Training"]
>>> print(" ".join(x))
Python Online Training

 


python return multiple values from functions

Python | Return multiple values from functions

>>> def A():
	return 2, 3, 4

>>> a, b, c = A()

>>> print(a, b, c)
2 3 4

 


Python Print String N times

Python | Print String N times

>>> s = 'Python'
>>> n = 5

>>> print(s * n)
PythonPythonPythonPythonPython

 


Python check the memory usage of an object

Python | Check the memory usage of  an object

>>> import sys
>>> x = 100

>>> print(sys.getsizeof(x))
28