I cut-and-paste from the definition for function Stats.get_extension_list()
<https://github.com/weewx/weewx/blob/v3.7.1/bin/weewx/cheetahgenerator.py#L537>.
You can see where trend_dict came from there. However, unless you plan to
use something like stats.trend in your search list extension (unlikely),
it, and several other parameters, can be safely left out. A more minimal
assignment for stats would look like:
stats = weewx.tags.TimeBinder(
db_lookup,
timespan.stop,
formatter=self.generator.formatter,
converter=self.generator.converter)
As for how often an SLE gets called, that depends on the usage pattern.
Without seeing the exact pattern you are using it's hard to say, but
something I see quite often is Cheetah expressions that look something like
this (this came up today):
#if $day.UV.has_data
<tr>
<td class="stats_label">UV</td>
#if $current.UV.raw <= 2.4
<td class="stats_data" style="background-color: limegreen">$current.UV</td>
#else if $current.UV.raw >= 2.5 and $current.UV.raw <= 5.4
<td class="stats_data" style="background-color: yellow">$current.UV</td>
#else if $current.UV.raw >= 5.5 and $current.UV.raw <= 7.4
<td class="stats_data" style="background-color: orange">$current.UV</td>
#else if $current.UV.raw >= 7.5 and $current.UV.raw <= 10.4
<td class="stats_data" style="background-color: red">$current.UV</td>
#else if $current.UV.raw > 10.5
<td class="stats_data" style="background-color: violet">$current.UV</td>
#end if
</tr>
#end if
This snippet will use the Current SLE up to eight times, just to get the UV
value. If the UV value is not available in the current record, that means
up to 8 SQL queries! A more efficient pattern is:
#if $day.UV.has_data
#set $current_UV = $current.UV.raw
<tr>
<td class="stats_label">UV</td>
#if $current_UV <= 2.4
<td class="stats_data" style="background-color: limegreen">$current.UV</td>
#else if $current_UV >= 2.5 and $current_UV <= 5.4
<td class="stats_data" style="background-color: yellow">$current.UV</td>
#else if $current_UV >= 5.5 and $current_UV <= 7.4
<td class="stats_data" style="background-color: orange">$current.UV</td>
#else if $current_UV >= 7.5 and $current_UV <= 10.4
<td class="stats_data" style="background-color: red">$current.UV</td>
#else
<td class="stats_data" style="background-color: violet">$current.UV</td>
#end if
</tr>
#end if
-tk
On Sun, Jun 25, 2017 at 9:49 AM, Thomas Carlin <[email protected]>
wrote:
> Thanks Tom, that looks like exactly what I need. Doing some testing this
> morning, I get an error on
> trend=trend_dict,
>
> NameError: global name 'trend_dict' is not defined
>
> Where does this dictionary originate?
>
> Unrelated to the original question, I noticed that my extension runs
> several times (7 i think) for each report generation. It's trivial to
> write a catch in so it only runs once, but i'm curious why this is. Could
> you shed any light on this?
>
> -Thomas
>
>
> On Saturday, June 24, 2017 at 8:25:07 PM UTC-6, Tom Keffer wrote:
>>
>> Not a simple question at all!
>>
>> Generally, yes, you can use something similar to the tags in your code by
>> following the same path through the objects. For example,
>>
>> $day.outTemp.latest
>>
>> can be obtained by using
>>
>> stats = weewx.tags.TimeBinder(
>> db_lookup,
>> timespan.stop,
>> formatter=self.generator.formatter,
>> converter=self.generator.converter,
>> week_start=self.generator.stn_info.week_start,
>> rain_year_start=self.generator.stn_info.rain_year_start,
>> trend=trend_dict,
>> skin_dict=self.generator.skin_dict)
>>
>> latest = stats.day.outTemp.latest
>>
>> This is basically all Cheetah is doing!
>>
>> Hope this helps.
>>
>> -tk
>>
>>
>> On Sat, Jun 24, 2017 at 8:39 AM, Thomas Carlin <[email protected]>
>> wrote:
>>
>>> Good morning everyone,
>>>
>>> I have a custom search list extension that I am working on to do some
>>> analysis on my collected data, and I have it to the point that I am pulling
>>> the data out, and can manipulate it, but to do so, I had to define my own
>>> timespan/binder inside my script. (The historygenerator extension does the
>>> same thing).
>>>
>>> Is there any way to use the weewx defined 'latest' or 'current'
>>> timespan inside my python extension? Please forgive me if this is a simple
>>> question, the only programing experience that I have is self-inflicted, and
>>> far from complete.
>>>
>>> Thank you!
>>>
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>>
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