
Python MongoDB Tutorial – How to Create a Collection with PyMongo
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MongoDB is a popular NoSQL database that stores data in flexible, JSON-like documents. In this tutorial, you’ll learn how to create a collection in MongoDB using Python and the PyMongo
library, including best practices and code examples.
Table of Contents
-
What Is a Collection in MongoDB?
-
Why Collections Matter
-
Prerequisites
-
Installing PyMongo
-
Connecting to MongoDB
-
Creating a Database
-
Creating a Collection
-
Inserting a Document (Triggers Creation)
-
Verifying Collection Creation
-
Full Working Example
-
Tips and Common Pitfalls
1. What Is a Collection in MongoDB?
A collection in MongoDB is similar to a table in a relational database. It is a group of MongoDB documents, which are stored in a database.
Each document in a collection can have a different structure, allowing for flexible schema design.
❓ 2. Why Collections Matter
-
Collections organize related data (like tables in SQL)
-
You query, update, and manage data within collections
-
Collections are automatically created when data is inserted
⚙️ 3. Prerequisites
-
Python installed (3.x recommended)
-
MongoDB server running locally or via Atlas
-
pymongo
installed
4. Installing PyMongo
Install the official MongoDB Python driver:
pip install pymongo
5. Connecting to MongoDB
Use MongoClient
to connect to a MongoDB server.
Local MongoDB Connection
import pymongo
client = pymongo.MongoClient("mongodb://localhost:27017/")
Remote MongoDB (MongoDB Atlas)
client = pymongo.MongoClient("mongodb+srv://username:[email protected]/?retryWrites=true&w=majority")
6. Creating a Database
Specify or create a database:
db = client["mydatabase"]
If the database doesn't exist, MongoDB will create it when you insert data into a collection.
7. Creating a Collection
You can create a collection explicitly using:
collection = db.create_collection("customers")
⚠️ This will throw an error if the collection already exists. To avoid this, check first:
if "customers" not in db.list_collection_names():
db.create_collection("customers")
Alternatively, you can implicitly create a collection just by accessing it and inserting data:
collection = db["customers"] # This doesn't create the collection yet
✍️ 8. Inserting a Document (Triggers Creation)
If using implicit creation, inserting a document will cause the collection to be created:
collection.insert_one({"name": "Alice", "email": "[email protected]"})
✅ 9. Verifying Collection Creation
You can list all collections in the database to confirm:
print(db.list_collection_names())
If "customers"
appears, your collection was successfully created.
10. Full Working Example
import pymongo
# Connect to MongoDB
client = pymongo.MongoClient("mongodb://localhost:27017/")
# Create a database
db = client["mydatabase"]
# Check if collection exists
if "customers" not in db.list_collection_names():
db.create_collection("customers")
print("Collection 'customers' created.")
else:
print("Collection already exists.")
# Insert a document (optional)
customer = {"name": "Alice", "email": "[email protected]"}
db["customers"].insert_one(customer)
# Verify
print("Collections:", db.list_collection_names())
Output:
Collection 'customers' created.
Collections: ['customers']
11. Tips and Common Pitfalls
Tip or Pitfall | Recommendation |
---|---|
Collection not showing | MongoDB won't create it until data is inserted |
Collection already exists error | Use list_collection_names() to check before creating |
Forgetting to insert | Implicit creation needs at least one document |
NoSQL schema | MongoDB collections don’t enforce strict schemas – be cautious about inconsistent data |
Conclusion
Creating a collection in MongoDB using Python is simple with the help of the pymongo
library. Whether you choose to create it explicitly or rely on implicit creation via document insertion, MongoDB’s flexibility makes it easy to structure your data your way.
Collections are the foundation of any MongoDB application—get them right, and you’ll have a solid structure for managing your data efficiently.
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=3Hence, 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