新手：Django：在传递给模板之前，将计算结果添加到Queryset [英] Newbie: Django : Adding calculated results to Queryset before passing to template

问题描述

我有一个现有的DB表（只读访问），我的已经使用网址，视图，模型和所有好的东西成功地显示在网页上的内容。

我遇到的挑战是不包含所有信息需要显示。该表包含列，sampletime，samplevalue，sampleresult的测试结果。我需要根据我从这些列中计算的数据显示不同的数据。

我的最终目标是使用 flotr 。现在，Id很乐意将我需要的数据转储到网页上的一个表（所以我可以可视化所得到的数据）

什么ID要传递给模板是

• jssampletime（sampletime datetime
  对象转换为javascript epoch
  ms）


• resultvalue（滚动和+ - 基于sampleresult是否好的抽样值）

我很好使用def函数创建jssampletime和resultvalue。我想我会将这些函数添加到views.py

我想我需要在views.py中迭代查询集，并将结果存储在我传给模板的字典这样的东西（代码未测试）。

views.py

 ＃views.py 
＃Sudo代码来解决问题
从django.shortcuts import render_to_response 
 from thing.reporter.models import Samples 
 
 def _datetime_to_js （sampletime）：
＃..日期转换epoch magic 
 return jsd_result 
 
 def _rolling_sum（samplevalue，sampleresult）：
＃.. summing magic 
 return sum_result 
 
 def dumptable（request）：＃由urls.py 
调用的def object_list = Samples.objects.all（）
 
 list_for_template = [ ] 
对于object_list中的行：
 jssampletime = _datetime_to_js（row.sampletime）
 resultvalue = _rolling_sum（row.samplevalue，row.sampleresult）
 list_for_template.append（{'jssampletime' ：jssampletime，'resultvalue'：resultvalue}）
 
返回render_to_response（'tabledump.html'，{'result_list'：list_for_templa te}）
  

tabledump.html

 ＃tabledump.html template 
 {％block content％} 
< h2>结果转储到页面进行测试< / h2> 
< ul> 
< table> 
 {result for result_list％} 
< tr> 
< td> {{result.jssampletime}}< / td> 
< td> {{result.resultvalue}}< / td> 
< / tr> 
 {％endfor％} 
< / table> 
< / ul> 
 {％endblock％} 
  

我认为这会工作，但我不知道是否Django MVC的方式。

是的，我，

• 结果我需要在views.py中通过查询查询结果进行交互？


• 将我的结果传递给一个模板作为
  的列表（是一个查询超过
  那个）？

我想我在寻找一些方向和代码提示。
我在正确的路上吗？有没有更好的方法？

解决方案

如果您显示的信息在一个模型中，为什么不只是添加属性/方法模型显示您需要摆脱的任何信息？然后，您可以将实际的模型列表/查询集传递给您的模板，并将方法称为属性。

例如

  class MyModel（models.Model）：
 model_field = models.CharField（max_length = 255）
 
 @property 
 def calculate_field（自我）：
 return self._do_calculation（self.model_field）
  

如果您需要访问状态变量在你的循环中，不要忘记，你可以将任何属性附加到一个python对象。这可以是非常有用的。所以在你看来，你可能会有这样的东西：

  for object in object_list：
＃update some variable we want to在模板中使用
 row.newly_added_field = run_calculation（row，somevariable）
  

可以在模板中访问：

  {％for result in result_list％} 
< tr> 
<！ - 一些直接显示模型的东西 - > 
< td> {{result.calculated_field}}< / td> 
< td> {{result.newly_added_field}}< / td> 
< / tr> 
 {％endfor％} 
  

Its day two of my new life with Django, please excuse the simplicity of my question.

I have an existing DB table(read-only access) that I have successfully displayed the contents of on a webpage using urls, views, models and all that good stuff.

The challenge I have is the table does not contain all the information I need to display. The table contains test results with the columns, sampletime, samplevalue, sampleresult. I need to display different data based on what I calculate from those columns.

My end goal is to display this info as a time series graph using flotr. For now Id be happy to just dump the data I need to a table on a web page.(So I can visualize the resulting data)

What Id like to pass to the template is,

• jssampletime(the sampletime datetime object converted to javascript epoch ms)
• resultvalue(rolling sum+- of samplevalue based on whether sampleresult was good or bad)

I'm fine with creating jssampletime and resultvalue using def functions. I presume I would add these functions to views.py

I guess what I need to do iterate over the a querySet in views.py and store the results in a list of dictionaries which I pass to the template. Something like this(code not tested).

views.py

# views.py
# Sudo code to assit in asking the question
from django.shortcuts import render_to_response
from thing.reporter.models import Samples

def _datetime_to_js(sampletime):
    #.. date conversion epoch magic
    return jsd_result

def _rolling_sum(samplevalue,sampleresult):
    #.. summing magic
    return sum_result

def dumptable(request): # The def that is called by urls.py
    object_list = Samples.objects.all()

    list_for_template = []
    for row in object_list:
        jssampletime = _datetime_to_js(row.sampletime)
        resultvalue  = _rolling_sum(row.samplevalue,row.sampleresult) 
        list_for_template.append({'jssampletime':jssampletime,'resultvalue':resultvalue})   

    return render_to_response('tabledump.html', {'result_list': list_for_template})

tabledump.html

# tabledump.html template
{% block content %}
    <h2>Results dumped to page for testing</h2>
    <ul>
    <table>
    {% for result in result_list %}
        <tr>
        <td>{{ result.jssampletime }}</td>
        <td>{{ result.resultvalue }}</td>
        </tr>
    {% endfor %}
    </table>
    </ul>
{% endblock %}

I think this would work but Im not sure if it is the Django MVC way.

Is it right that I,

• calculate the result I need in views.py by interating over a queryset result?
• pass my result to a template as a list of dict(is a queryset more than that)?

I guess Im looking for some direction and code tips. Am I on the right path ? Is there a better way ?

解决方案

If the information you are displaying is in a model why not just add properties/methods to the model to display whatever information you need to get out of it? Then you can pass the actual model list / query set to your template and call the methods as properties.

e.g.

class MyModel(models.Model):
    model_field = models.CharField(max_length=255)

    @property
    def calculated_field(self):
        return self._do_calculation(self.model_field)

If you need access to state variables in your loop, don't forget that you can attach any property to a python object. This can be extremely useful. So in your view you could have something like:

for row in object_list:
    # update some variable we want to use in the template
    row.newly_added_field = run_calculation(row, somevariable)

Both of these could then be accessed within the template:

{% for result in result_list %}
    <tr>
    <!-- some stuff that displays the model directly -->
    <td>{{ result.calculated_field}}</td>
    <td>{{ result.newly_added_field}}</td>
    </tr>
{% endfor %}

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