Querying multiple columns efficiently SQLAlchemy ORM

Question

I am trying to do a query using SQL Alchemy, but I want to "select" 20 columns from a table that contains around 57, I know that the method to do this is

session.query(Table.col1, Table.col2, Table.col3, Table.col4......).all()

But it is so inefficient and for sure there is a much better way for doing this.

What I have tried unsuccessfully, but it is getting very close is:

# "columns" is a dictionary that contains all the column names, it looks more or less like this (shorter version

columns = {"Account ID": "AR3",
         "Account Origination Month": "AR55",
         "Origination balance": "AR66",
         "Product": "AR10",
         "Repayment Type": "AR69",
         "Original Loan Term (in months)": "AR61",
         "Initial Product Term (in months)": "AR106",
         "Initial rate/margin": "AR109",
         "Initial Rate Type": "AR107",
         "Reversion margin": "AR119",}



columns_sqla = ", ".join(["Table."+str(value) for key, value in columns.items()])

>>> columns_sqla

'BoE.AR3, BoE.AR55, BoE.AR66, BoE.AR10, BoE.AR69, BoE.AR61, BoE.AR106, BoE.AR109, BoE.AR107, BoE.AR119'

Then I do:

session.query(columns_sqla)

But it throws an error because it is a string and it doesn't recognise it.

Answer 1

You can try variable unpacking mechanism as mentioned below:

session.query(*columns.values()).all()

Also run the below code for more understating.

Tuple = lambda *args: args
Dict = lambda **kwargs: kwargs
Print(Tuple(*columns))# PRINT KEYS
Print(columns.Keys())# PRINT KEYS
Print(Dict(**columns))# PRINT DICT ITEMS
Print(columns)# PRINT DICT ITEMS