comfortly "with" for Connection() #946

dashedman · 2021-01-11T12:14:57Z

dashedman
Jan 11, 2021

class Connection():
    ...
    def __enter__(self):
        if not self.open:
            self.ping(reconnect=True)
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.close()
        if exc_val:
            raise
            
            
conn = Connection(...)

#for every request use
with conn, conn.cursor() as cur:
    ... #first request
    
...
time.sleep(many) #many times without requests
...

with conn, conn.cursor() as cur:
    ... #second request

# etc

if db drop the connection, context manager with do a reconnect in __enter__()

methane · 2021-01-12T02:07:37Z

methane
Jan 12, 2021
Maintainer

What is the difference from this?

def create_connection():
    return pymysql.connect(...)

with create_connection() as conn:
    # first use

with create_connection() as conn:
    # second use

I don't want to implement "maybe convenient for some people" behaviors. Such behaviors make long-term maintenance cost. Convenient features must be implemented in the higher layer as possible. Low-level library must focus on low-level.

3 replies

dashedman Jan 12, 2021
Author

So, why you adding implement for "with" without proffit? Just for ignore of exceptions? - it's bad behavior for low-level library :c

methane Jan 13, 2021
Maintainer

So, why you adding implement for "with" without profit?

Have you ever used file objects? Using with for closing file object is best practice. And file objects don't provide "implicit reopen" as you suggested:

f = open(path)

with f:
    d1 = f.read()

with f:  # open again; this is not supported.
    d2 = f.read()

Do you think it is without profit? It's bad behavior?

dashedman Jan 14, 2021
Author

It's not a low-level library)

I undestand you.
In pep 343 -- The "with" Statement(Caching Context Managers), says "Many context managers (such as files and generator-based contexts) will be single-use objects." Many but not all...

I'll close this disscusion

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comfortly "with" for Connection() #946

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dashedman Jan 11, 2021

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methane Jan 12, 2021 Maintainer

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dashedman
Jan 11, 2021

Replies: 1 comment 3 replies

methane
Jan 12, 2021
Maintainer

dashedman Jan 12, 2021
Author

methane Jan 13, 2021
Maintainer

dashedman Jan 14, 2021
Author