How to add a function after Python with..as

This is an example of using pandas to read data from sqlite.

 from sqlalchemy import create_engine
import pandas aspd

engine=create_engine('sqlite://:memory:')

with engine.connect() as conn, conn.begin():
    data=pd.read_sql_table('data',conn)

I know the basic usage of the with statement, but I have never seen a function call after as.I would appreciate it if you could tell me the role of conn.begin().

python sql sqlalchemy

2022-11-05 00:00

2 Answers

It's not that difficult, it's just that there's no as on the back, equivalent to the following.
(.begin() is the beginning of the transaction.)

with engine.connect() as conn:
    with conn.begin():
        pass# Something to be done

You can also do these things

with engine.begin() as conn:
    pass# Something to be done

Note: (docs.sqlalchemy.org) Working with Engines and Connections:Using Transactions

2022-11-05 00:00

Multiple context managers can be used in With statements.They act as if they were nested.

When multiple elements exist, the context manager proceeds as if multiple with statements were nested:

 with A() as a, B() as b:
    SUITE

This is equivalent to:

 with A() as a:
    with B() as b:
        SUITE

Interviewer: with statement

The code for the question is the omission of asb in the example above.In other words,

with engine.connect() as conn:
    with conn.begin():

will be

2022-11-05 00:00

If you have any answers or tips

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