How to set primary key auto increment in SqlAlchemy orm

Question

I tired to use the SqlAlchemy orm to build the api to insert the values into database from uploaded excel files. when I tested on the codes it kept showing the error:

TypeError: __init__() missing 1 required positional argument: 'id'

I’ve updated the id key to primary key, auto increment, unique and unsigned in my local MySql data base. I believe the system cannot insert the primary key automatically because it works if I assign the value to id manually

transaction_obj = Transaction(id=1, name="David", date="2018-03-03", 
                product="fruit", quantity=20, amount=12.55)

Here is model.py

from sqlalchemy import Table, MetaData, Column, Integer, String, DATE, DECIMAL,ForeignKey, DateTime
from sqlalchemy.orm import mapper

metadata = MetaData()


customers = Table('customers', metadata,
                  Column('id', Integer, primary_key=True),
                  Column('name', String(20)),
                  Column('phone', String(20)),
                  Column('address', String(45)),
                  Column('source_from', String(45))
                  )


class Customers(object):
    def __init__(self, name, phone, address, source_from):
        self.name = name
        self.phone = phone
        self.address = address
        self.source_from = source_from

    def __repr__(self):
        return "<Customer(name='%s', phone='%s', address='%s', " 
               "source_from='%s')" % (self.name, self.phone, self.address,
                                      self.source_from)


mapper(Customers, customers)



transaction = Table('transaction', metadata,
                    Column('id', Integer, primary_key=True),
                    Column('name', String(20)),
                    Column('date', DateTime),
                    Column('product', String(20)),
                    Column('quantity', Integer),
                    Column('amount',DECIMAL(2))
                    )


class Transaction(object):
    def __index__(self, name, date, product, quantity, amount):
        self.name = name
        self.date = date
        self.product = product
        self.quantity = quantity
        self.amount = amount

    def __repr__(self):
        return "<Transaction(name='%s', date='%s', product='%s'," 
               "quantity='%s', amount='%s')>" % (self.name, self.date,
                                                 self.product, self.quantity,
                                                 self.amount)


mapper(Transaction, transaction)

Here is my test coding: test.py

import json
import os
import os
import json
from sqlalchemy import create_engine
import config
import pandas as pd

conn = config.conn_str

def tran_test():
    engine = create_engine(conn)
    Session_class = sessionmaker(bind=engine) 
    Session = Session_class  
    # generate the object for the data we would like to insert

    transaction_obj = Transaction(name="David", date="2018-03-03", 
                product="fruit", quantity=20, amount=12.55)
    Session.add(transaction_obj)

    Session.commit()

def test_uploaded_file(file):
    df = pd.read_excel(file)
    return df.info()


if __name__ == '__main__':
    # set_env_by_setting('prod')
    # conn_str = os.environ.get('ConnectionString')
    # print(conn_str)
    # test_uploaded_file("-1.xlsx")
    tran_test()

I’m using SQLAlchemy==1.2.10, PyMySQL==0.9.2.
I’m doubting if I’m using the wrong format in model.py. Please advise. Thx.

Asked By: Chenney Huang

||

Source

Answer 1

While I’m not sure about the pattern you are using, (manually mapping to your table classes) I think you would have a much easier time making use of declarative_base which does this for you.

from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()

Then make sure your models inherit Base

from sqlalchemy import (
    Column,
    Integer,
    String
)


    class Customers(Base):
        __tablename__ = 'customer'
        id = Column(Integer, primary_key=True) # Auto-increment should be default
        name = Column(String(20))
        # Etc.

        def __repr__(self):
            return "<Customer(name='%s', phone='%s', address='%s', " 
                   "source_from='%s')" % (self.name, self.phone, self.address,
                                          self.source_from)

And finally use Base to create your table:

Base.metadata.create_all(engine)

Here is a good reference to basic declarative use cases. It gets a little more complicated depending on how you are scaffolding your app but its a great starting point:
http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/basic_use.html

Answered By: Andrew Riess

How to set primary key auto increment in SqlAlchemy orm

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