Re: Cannot step through asynchronous iterator manually

On Sat, Jan 30, 2016 at 7:22 PM, Frank Millman wrote: > We had a recent discussion about the best way to do this, and ChrisA > suggested the following, which I liked - > >cur.execute('SELECT ...) >try: >row = next(cur) >except StopIteration: ># row

Cannot step through asynchronous iterator manually

Hi all To loop though an iterator one usually uses a higher-level construct such as a 'for' loop. However, if you want to step through it manually you can do so with next(iter). I expected the same functionality with the new 'asynchronous iterator' in Python 3.5, but I cannot find it. I

Re: Cannot step through asynchronous iterator manually

On Sun, Jan 31, 2016 at 6:42 AM, Michael Torrie wrote: > On 01/30/2016 01:22 AM, Frank Millman wrote: >> There are times when I want to execute a SELECT statement, and test for >> three possibilities - >> - if no rows are returned, the object does not exist >> - if one

Re: Cannot step through asynchronous iterator manually

On 01/30/2016 02:19 PM, Chris Angelico wrote: > Efficiency. That's a fine way of counting actual rows in an actual > table. However, it's massive overkill to perform an additional > pre-query for something that's fundamentally an assertion (this is a > single-row-fetch API like "select into", and

Re: Cannot step through asynchronous iterator manually

On 01/30/2016 01:22 AM, Frank Millman wrote: > There are times when I want to execute a SELECT statement, and test for > three possibilities - > - if no rows are returned, the object does not exist > - if one row is returned, the object does exist > - if more that one row is returned,

Re: Cannot step through asynchronous iterator manually

On Sun, Jan 31, 2016 at 8:52 AM, Michael Torrie wrote: > On 01/30/2016 02:19 PM, Chris Angelico wrote: >> Efficiency. That's a fine way of counting actual rows in an actual >> table. However, it's massive overkill to perform an additional >> pre-query for something that's

Re: Cannot step through asynchronous iterator manually

"Oscar Benjamin" wrote in message news:cahvvxxsa0yq4voyy6qycgxxvpl5zzgm8muui+1vmezd8crg...@mail.gmail.com... The simplest thing would just be to call list(cur) but I realise that you don't want to consume more than 2 rows from the database so just use islice: rows = list(islice(cur, 2)) #

Re: Cannot step through asynchronous iterator manually

On 30 January 2016 at 13:45, Frank Millman wrote: > "Oscar Benjamin" wrote in message > news:cahvvxxsa0yq4voyy6qycgxxvpl5zzgm8muui+1vmezd8crg...@mail.gmail.com... >> >> >> The simplest thing would just be to call list(cur) but I realise that > > you don't want to consume more

Re: Cannot step through asynchronous iterator manually

On 30 January 2016 at 16:42, Ian Kelly wrote: >> AFAICT there's no generator-function-style syntax for writing an async >> iterator so you'd have to make a class with the appropriate methods if >> you wanted to be able to loop over aslice with async for. > > Before you go

Re: Cannot step through asynchronous iterator manually

On Jan 30, 2016 7:13 AM, "Oscar Benjamin" wrote: > > I haven't used PEP 492 yet but what about: > > async def aslice(asynciterator, end): > if end == 0: > return [] >items = [] >async for item in asynciterator: >items.append(item) >

Re: Cannot step through asynchronous iterator manually

2016-01-30 11:51 GMT+01:00 Frank Millman : > "Chris Angelico" wrote in message > news:CAPTjJmoAmVNTCKq7QYaDRNQ67Gcg9TxSXYXCrY==s9djjna...@mail.gmail.com... > > >> On Sat, Jan 30, 2016 at 7:22 PM, Frank Millman >> wrote: >> > We had a recent discussion

Re: Cannot step through asynchronous iterator manually

"Maxime S" wrote in message news:CAGqiJR8yUdd1u7j0YHS-He_v4uUT-ui=PpiX=n_G=ntt8zn...@mail.gmail.com... I might be a bit off-topic, but why don't you simply use cursor.rowcount? I just tried that on sqlite3 and pyodbc, and they both return -1. I think that it only works with

Re: Cannot step through asynchronous iterator manually

On Sat, Jan 30, 2016 at 7:02 PM, Ian Kelly wrote: > On Jan 29, 2016 11:04 PM, "Frank Millman" wrote: >> >> Hi all >> >> To loop though an iterator one usually uses a higher-level construct such > as a 'for' loop. However, if you want to step through it

Re: Cannot step through asynchronous iterator manually

"Ian Kelly" wrote in message news:CALwzid=ssdsm8hdan+orj54a_jeu9wc8103iqgkaah8mrj-...@mail.gmail.com... On Jan 29, 2016 11:04 PM, "Frank Millman" wrote: > > Hi all > > To loop though an iterator one usually uses a higher-level construct > such as a 'for' loop. However,

Re: Cannot step through asynchronous iterator manually

On Jan 29, 2016 11:04 PM, "Frank Millman" wrote: > > Hi all > > To loop though an iterator one usually uses a higher-level construct such as a 'for' loop. However, if you want to step through it manually you can do so with next(iter). > > I expected the same functionality with

Re: Cannot step through asynchronous iterator manually

"Chris Angelico" wrote in message news:CAPTjJmoAmVNTCKq7QYaDRNQ67Gcg9TxSXYXCrY==s9djjna...@mail.gmail.com... On Sat, Jan 30, 2016 at 7:22 PM, Frank Millman wrote: > We had a recent discussion about the best way to do this, and ChrisA > suggested the following, which I

Re: Cannot step through asynchronous iterator manually

To address the original question, I don't believe a next() equivalent for async iterables has been added to the standard library yet. Here's an implementation from one of my projects that I use to manually get the next value: https://bpaste.net/show/e4bd209fc067. It exposes the same interface as

Re: Cannot step through asynchronous iterator manually

> Any particular reason not to use the classic sentinel object model? None that I can remember. I would use the sentinel pattern if I were writing it again today. > Also curious is that you raise a new StopAsyncIteration from the original one, rather than just reraising the original. I assume

Re: Cannot step through asynchronous iterator manually

On Sat, Jan 30, 2016 at 11:35 PM, Kevin Conway wrote: > To address the original question, I don't believe a next() equivalent for > async iterables has been added to the standard library yet. Here's an > implementation from one of my projects that I use to manually get

Re: Cannot step through asynchronous iterator manually

On 30 January 2016 at 08:22, Frank Millman wrote: > There are times when I want to execute a SELECT statement, and test for > three possibilities - >- if no rows are returned, the object does not exist >- if one row is returned, the object does exist >- if more

Re: Cannot step through asynchronous iterator manually

Michael Torrie wrote: I'm not sure how SQLite handles it, or even what the SQL spec says, but I know in MySQL you could do something like this: SELECT count(id) as row_count,`tablename`.* FROM `tablename` WHERE condition I don't think that's strictly valid SQL. I know of at least one SQL

Re: Cannot step through asynchronous iterator manually

On Sun, Jan 31, 2016 at 9:05 AM, Michael Torrie wrote: > On 01/30/2016 02:57 PM, Michael Torrie wrote: >> SELECT count(some_id_field),field1,field2,field3 FROM wherever WHERE >> conditions >> >> If the first column (or whatever you decide to alias it as) contains a >> count,

Re: Cannot step through asynchronous iterator manually

On 01/30/2016 02:57 PM, Michael Torrie wrote: > SELECT count(some_id_field),field1,field2,field3 FROM wherever WHERE > conditions > > If the first column (or whatever you decide to alias it as) contains a > count, and the rest of the information is still there. If count is 1, > then the row is

Re: Cannot step through asynchronous iterator manually

On Sun, Jan 31, 2016 at 8:57 AM, Michael Torrie wrote: > On 01/30/2016 02:19 PM, Chris Angelico wrote: >> where the ... is the full original query. In other words, the whole >> query has to be run twice - once to assert that there's exactly one >> result, and then a second time

Re: Cannot step through asynchronous iterator manually

On 01/30/2016 03:06 PM, Chris Angelico wrote: > That actually violates the SQL spec. Some servers will accept it, > others won't. (You're not supposed to mix column functions and > non-column functions.) Are you sure? Wikipedia is not always the most accurate place, but they have several clear

Re: Cannot step through asynchronous iterator manually

On Sun, Jan 31, 2016 at 9:19 AM, Michael Torrie wrote: > On 01/30/2016 03:06 PM, Chris Angelico wrote: >> That actually violates the SQL spec. Some servers will accept it, >> others won't. (You're not supposed to mix column functions and >> non-column functions.) > > Are you

Re: Cannot step through asynchronous iterator manually

On 01/30/2016 02:19 PM, Chris Angelico wrote: > where the ... is the full original query. In other words, the whole > query has to be run twice - once to assert that there's exactly one > result, and then a second time to get that result. The existing > algorithm ("try to fetch a row - if it fails