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<title>[django] Variables and attributes may not begin with underscores - Mozillazg's Blog</title>
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<meta name="description" content="当尝试在模板中调用以下划线开头的对象时，会报如下类似错误： TemplateSyntaxError at / Variables and attributes may not begin with underscores: 'user._meta.get_field('name').help_text' 解决方法就是，将调用以下划线开头的对象的操作封装到模板过滤器中。 如何创建自定义模板过滤器 在 models.py 文件所在目录新建一个 templatetags 目录: hello/ models.py templatetags/ hello_extras.py __init__.py views.py hello_extras.py 中保存着我们自定义的模板过滤器。 在 hello_extras.py 文件的开头需要包含如下代码： from django import template register = template ..." />
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<meta property="og:description" content="当尝试在模板中调用以下划线开头的对象时，会报如下类似错误： TemplateSyntaxError at / Variables and attributes may not begin with underscores: 'user._meta.get_field('name').help_text' 解决方法就是，将调用以下划线开头的对象的操作封装到模板过滤器中。 如何创建自定义模板过滤器 在 models.py 文件所在目录新建一个 templatetags 目录: hello/ models.py templatetags/ hello_extras.py __init__.py views.py hello_extras.py 中保存着我们自定义的模板过滤器。 在 hello_extras.py 文件的开头需要包含如下代码： from django import template register = template ..."/>
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[django] Variables and attributes may not begin with underscores
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2013-01-17
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<a href="https://mozillazg.com/category/django.html">django</a>
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<p>当尝试在模板中<strong>调用以下划线开头的对象时</strong>，会报如下类似错误：</p>
<blockquote>
<p>TemplateSyntaxError at /</p>
<p>Variables and attributes may not begin with underscores: 'user._meta.get_field('name').help_text'</p>
</blockquote>
<p>解决方法就是，将调用以下划线开头的对象的操作封装到模板过滤器中。</p>
<h2 id="_1">如何创建自定义模板过滤器</h2>
<p>在 models.py 文件所在目录新建一个 templatetags 目录:</p>
<div class="codehilite"><pre><span class="n">hello</span><span class="o">/</span>
<span class="n">models</span><span class="p">.</span><span class="n">py</span>
<span class="n">templatetags</span><span class="o">/</span>
<span class="n">hello_extras</span><span class="p">.</span><span class="n">py</span>
<span class="n">__init__</span><span class="p">.</span><span class="n">py</span>
<span class="n">views</span><span class="p">.</span><span class="n">py</span>
</pre></div>
<p>hello_extras.py 中保存着我们自定义的模板过滤器。</p>
<p>在 hello_extras.py 文件的开头需要包含如下代码：</p>
<div class="codehilite"><pre><span class="kn">from</span> <span class="nn">django</span> <span class="kn">import</span> <span class="n">template</span>
<span class="n">register</span> <span class="o">=</span> <span class="n">template</span><span class="o">.</span><span class="n">Library</span><span class="p">()</span>
</pre></div>
<p>本例中我们将定义一个 help_text 过滤器，用于获取 models 中字段的 help_text 的值，所以 hello_extras.py 的内容为：</p>
<div class="codehilite"><pre><span class="kn">from</span> <span class="nn">django</span> <span class="kn">import</span> <span class="n">template</span>
<span class="n">register</span> <span class="o">=</span> <span class="n">template</span><span class="o">.</span><span class="n">Library</span><span class="p">()</span>
<span class="nd">@register.filter</span>
<span class="k">def</span> <span class="nf">help_text</span><span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="n">arg</span><span class="p">):</span>
<span class="k">return</span> <span class="n">value</span><span class="o">.</span><span class="n">_meta</span><span class="o">.</span><span class="n">get_field</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span><span class="o">.</span><span class="n">help_text</span>
</pre></div>
<p>在模板中使用自定义过滤器时，要记得导入过滤器：</p>
<div class="codehilite"><pre><span class="cp">{%</span> <span class="k">load</span> <span class="nv">hello_extras</span> <span class="cp">%}</span><span class="x"></span>
</pre></div>
<p>本例的模板文件：</p>
<div class="codehilite"><pre><span class="cp">{%</span> <span class="k">load</span> <span class="nv">hello_extras</span> <span class="cp">%}</span>
<span class="cp">{%</span> <span class="k">for</span> <span class="nv">user</span> <span class="k">in</span> <span class="nv">users</span> <span class="cp">%}</span>
<span class="nt"><p></span><span class="cp">{{</span> <span class="nv">user</span><span class="o">|</span><span class="nf">help_text</span><span class="s2">:"name"</span> <span class="cp">}}</span>： <span class="cp">{{</span> <span class="nv">user.name</span> <span class="cp">}}</span><span class="nt"></p></span>
<span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span>
</pre></div>
<p>models 文件节选：</p>
<div class="codehilite"><pre><span class="k">class</span> <span class="nc">User</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
<span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">50</span><span class="p">,</span> <span class="n">help_text</span><span class="o">=</span><span class="s">u'姓名'</span><span class="p">)</span>
</pre></div>
<p>模板渲染结果：</p>
<blockquote>
<p>姓名：tom</p>
<p>姓名：jim</p>
<p>姓名：eric</p>
</blockquote>
<p>测试项目下载：<a href="/static/downloads/2013.01.17.mysite.tar.gz">mysite.tar.gz</a> ，测试环境：django 1.4.3。</p>
<h2 id="_2">参考</h2>
<ul>
<li><a href="http://stackoverflow.com/questions/4279905/access-django-model-fields-label-and-help-text">access django model fields label and help_text - Stack Overflow</a></li>
<li><a href="http://stackoverflow.com/questions/6571649/model-name-of-objects-in-django-templates">Model name of objects in django templates - Stack Overflow</a></li>
<li><a href="https://docs.djangoproject.com/en/dev/howto/custom-template-tags/">Custom template tags and filters | Django documentation | Django</a></li>
</ul>
</div>
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<p>Related Posts:</p>
<ul>
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<li><a href="https://mozillazg.com/2013/02/django-typeerror-decod-argument-1-must-be-string-not-none.html">[django] 创建后台超级用户时出现 TypeError: decode() argument 1 must be string, not None 错误</a></li>
<li><a href="https://mozillazg.com/2013/10/django-TypeError-delete-got-an-unexpected-keyword-argument-using.html">[django]修复 "TypeError: delete() got an unexpected keyword argument 'using'"</a></li>
<li><a href="https://mozillazg.com/2013/04/django-custom-model-display-name-on-admin-pages.html">[django]自定义 model 在后台显示的名称</a></li>
<li><a href="https://mozillazg.com/2014/03/django-save-uploaded-file-with-utf8-encoding-by-custom-model-field.html">[django]通过自定义 Model Field 的方式将上传的文本文件按 UTF-8 编码保存</a></li>
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