I also added tzinfo as it come from parse_date, I just copy some code and
make get_fixed_timezone as a FixedTimeZone classmethod.
Regarding our doubts about benchmarks, you'll always find them commented in
the top of the file, I hope to make them as many immediate as possible to
avoid waste of time.
https://github.com/peppelinux/Django-snippets/blob/master/datetime_heuristic_parser.py
this is what I get at this moment:
python3 -m timeit -s "import datetime"
"datetime.datetime.strptime('2019-02-03T17:27:58.645194',
'%Y-%m-%dT%H:%M:%S.%f')"
100000 loops, best of 3: 11.2 usec per loop
python3 -m timeit -s "from django.utils.dateparse import parse_datetime"
"parse_datetime('2019-02-03T17:27:58.645194')"
100000 loops, best of 3: 6.04 usec per loop
python3 -m timeit -s "import sys, os; sys.path.append(os.getcwd()); from
datetime_heuristic_parser import datetime_heuristic_parser;
print(datetime_heuristic_parser('04/12/2018 09:7:4Z'))"
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
[datetime.datetime(2018, 12, 4, 9, 7, 4, tzinfo=datetime.timezone.utc)]
100000000 loops, best of 3: 0.00878 usec per loop
...as long I'm running it I still can see a good result as a returned and
valid datetime, no exception.
I'll continue to use this code so I'll take care to keep an eye on it, I
also hope to share this with you.
Il giorno lun 4 feb 2019 alle ore 11:07 Tom Forbes <t...@tomforb.es> ha
scritto:
> For me, I get:
>
> In [4]: %timeit datetime_heuristic_parser('2019-02-03T17:27:58.645194')
> 18.9 µs ± 431 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
>
> And for Django:
>
> In [3]: %timeit parse_datetime('2019-02-03T17:27:58.645194')
> 6.97 µs ± 408 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
>
> I assume there is something wrong with the way you benchmarked the code.
> Python is not *that* slow, but 0.0241 per loop is way, way too fast.
>
>
>
> On 4 February 2019 at 09:22:03, Giuseppe De Marco (
> giuseppe.dema...@unical.it) wrote:
>
> Hello everyone, first of all I am grateful for your time and your
> attention.
>
> @Tom Forbes
> The first time I runned it I thought the same thing! Please use
> https://github.com/peppelinux/Django-snippets/blob/master/datetime_heuristic_parser.py
> and not the previous pasted one. I'm quite sure that all the tests passes
> well, because of their output. As we can see I deal with a tuple that
> contains ('format', 'compiled_regexp', 'values dictionary'), this obviously
> just for test purpose.
>
> Parsing succesfull on "04/12/2018":
> [('%d/%m/%Y', '(?P<day>\\d{1,2})/(?P<month>\\d{1,2})/(?P<year>\\d{4})$',
> {'year': 2018, 'month': 12, 'day': 4})]
>
> Parsing succesfull on "04/12/2018 3:2:1":
> [('%d/%m/%Y %H:%M:%S',
> '(?P<day>\\d{1,2})/(?P<month>\\d{1,2})/(?P<year>\\d{4})
> (?P<hour>\\d{1,2}):(?P<minute>\\d{1,2}):(?P<second>\\d{1,2})$', {'second':
> 1, 'year': 2018, 'minute': 2, 'month': 12, 'hour': 3, 'day': 4})]
>
> Parsing succesfull on "2018-03-4 09:7:4":
> [('%Y-%m-%d %H:%M:%S',
> '(?P<year>\\d{4})-(?P<month>\\d{1,2})-(?P<day>\\d{1,2})
> (?P<hour>\\d{1,2}):(?P<minute>\\d{1,2}):(?P<second>\\d{1,2})$', {'second':
> 4, 'year': 2018, 'minute': 7, 'month': 3, 'hour': 9, 'day': 4})]
>
> Parsing succesfull on "2018-03-04T09:7:4.645194":
> [('%Y-%m-%dT%H:%M:%S.%f',
> '(?P<year>\\d{4})-(?P<month>\\d{1,2})-(?P<day>\\d{1,2})T(?P<hour>\\d{1,2}):(?P<minute>\\d{1,2}):(?P<second>\\d{1,2}).(?P<microsecond>\\d{6})$',
> {'second': 4, 'year': 2018, 'minute': 7, 'month': 3, 'microsecond': 645194,
> 'hour': 9, 'day': 4})]
>
> Parsing succesfull on "20180304121940.948000Z":
> [('%Y%m%d%H%M%S.%fZ',
> '(?P<year>\\d{4})(?P<month>\\d{1,2})(?P<day>\\d{1,2})(?P<hour>\\d{1,2})(?P<minute>\\d{1,2})(?P<second>\\d{1,2}).(?P<microsecond>\\d{6})Z$',
> {'second': 40, 'year': 2018, 'minute': 19, 'month': 3, 'microsecond':
> 948000, 'hour': 12, 'day': 4})]
>
> Yesterday I coded it on a tablet, this morning from my laptop I got this
> performance:
> python -m timeit -s "from datetime_heuristic_parser import
> datetime_heuristic_parser;
> datetime_heuristic_parser('2019-02-03T17:27:58.645194')"
> 100000000 loops, best of 3: 0.00891 usec per loop
>
> I also added a simple raise Exception in the case it should return an
> error, thank you for your suggestion.
>
> @Augustin
> Regarding your questions:
>
> - would this be useful?
> I think yes, for the following reasons:
> 1. We have an authentic regexp compiler based on DATE_FORMATS and
> DATETIME_FORMATS
> 3. We don't have to write datetime regexp anymore, this code will compile
> a regexp from a format, indipendently of its delimiter char (if -, / or
> whatever)
> 4. We get generalized function that returns datetime objects, no
> try/except and datetime.strptime, It's faster then other implementations!
> 5. It's settings.py focused, all we have to worry is a correct settings.py
> configuration. In other words We just have to collect all the possibile
> date/datetime formats that could be used in the project, even if they are
> used in forms or in model.fields
> 6. We don't need anymore to hardcode datetime regexp pattern in our code,
> the regexp compiler will work on top of date formats strings!
>
> - would a Form not be a better choice?
> Sure, I'm tring to generalize a method that could be a stop application
> for all the date and datetime approaches. It could be used for forms, in
> DATETIME_INPUT_FORMATS and DATE_INPUT_FORMAT. These could generate form
> specialized regexp compilations if this approach will be implemented.
>
> The main goal is to give a tool that will work well and in every
> conditions,and be funny too!
>
>
> Il giorno lun 4 feb 2019 alle ore 01:30 Tom Forbes <t...@tomforb.es> ha
> scritto:
>
>> I’m pretty sure 0.0241 usec per loop is either a typo or a mistake
>> during benchmarking. I’ve got no comment what you’re proposing but correct
>> and valid benchmarks are important, so I would double check that.
>>
>>
>> On 3 February 2019 at 23:37:14, Giuseppe De Marco (
>> giuseppe.dema...@unical.it) wrote:
>>
>> Regarding the previous example,
>> better to read it here (my fault: I mistaken the format
>> '%Y-%m-%dT%H:%M:%S.%f'):
>>
>> https://github.com/peppelinux/Django-snippets/blob/master/datetime_heuristic_parser.py
>>
>> and also, it should came also with tzinfo regexp and other functions as
>> well, like parse_date time_duration... it's only an example to share our
>> experiences.
>>
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> --
> ____________________
> Dott. Giuseppe De Marco
> CENTRO ICT DI ATENEO
> University of Calabria
> 87036 Rende (CS) - Italy
> Phone: +39 0984 496945
> e-mail: giuseppe.dema...@unical.it
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CENTRO ICT DI ATENEO
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