Engine
- Python course
- Advanced
- Lesson 43/83
- 5 min
Learn the database engine with create_engine.
Engine
create_engine sets up SQLAlchemy's database connection. It takes a connection string and returns an Engine object. For an in-memory SQLite database, use sqlite:///:memory:.
from sqlalchemy import create_engine
engine = create_engine("sqlite:///:memory:")
print(engine.url)The Engine manages the connection pool; actual queries go through a Session. You create the Engine once in an application.
Connection string
The connection string specifies the database type and location. For SQLite, the form sqlite:///path is used; :memory: means an in-memory database.
# In-memory
engine = create_engine("sqlite:///:memory:")
# File-based
engine = create_engine("sqlite:///uyeler.db")For other databases, a string like postgresql://user:pass@host/db is used. SQLAlchemy picks the right driver from the string.
Practice Create Engine and print
Start with from sqlalchemy import create_engine. Define an engine with create_engine("sqlite:///:memory:"). Print the connection string with print(engine.url).
Starter code
# bring in create_engine from sqlalchemy
# define an engine with the in-memory sqlite string
# print the engine's urlSample solution
from sqlalchemy import create_engine
engine = create_engine("sqlite:///:memory:")
print(engine.url)Expected output
sqlite:///:memory:
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What parameter does create_engine use to connect?
- A file object
- A connection string Correct answer
- A class name
- A user name
Explanation: create_engine takes a connection string to connect to the database.
2 Complete the create_engine call
from sqlalchemy import create_engine
engine = create_engine("____")from sqlalchemy import create_engine
engine = create_engine("sqlite:///:memory:")Explanation: sqlite:///:memory: is an in-memory SQLite database.
3 Match the Engine concepts
| Term | Meaning |
|---|---|
create_engine |
Creates the engine |
engine.url |
Gives the connection string |
sqlite:///:memory: |
In-memory database |
Engine |
Manages the pool |