SQLAlchemy ER diagram in python 3

Question

Does anyone know a way to make an ER diagram from SQLAlchemy models in python 3. I found sqlalchemy_schemadisplay, which is python 2 because of pydot and ERAlchemy which is also python 2 only.

Answer 1

You can try eralchemy.

import matplotlib.pyplot as plt
import matplotlib.image as mpimg
import pandas as pd
from eralchemy import render_er

from sqlalchemy import (MetaData, Table, Column)    
metadata = MetaData()

# create your own model ....
users = Table('users', metadata,
    Column('user_id', Integer(), primary_key=True),
    Column('username', String(15), nullable=False, unique=True),
)    
orders = Table('orders', metadata,
    Column('order_id', Integer()),
    Column('user_id', ForeignKey('users.user_id')),
)
# add your own table ....

# Show ER model from here
filename = 'mymodel.png'
render_er(metadata, filename)
imgplot = plt.imshow(mpimg.imread(filename))
plt.rcParams["figure.figsize"] = (15,10)
plt.show()

Then it shows the model.

Those modules I used are:

Software Version
Python 3.4.5 64bit
IPython 5.1.0
OS Windows 10
sqlalchemy 1.1.5
eralchemy 1.1.0
matplotlib 2.0.0

Answer 2

As mentioned in an earlier answer, sqlalchemy_schemadisplay is a fantastically simple tool. Here's the basic how you would use it:

from sqlalchemy_schemadisplay import create_schema_graph
from sqlalchemy import MetaData

graph = create_schema_graph(metadata=MetaData('postgres://user:pwd@host/database'))
graph.write_png('my_erd.png')