Question

Django 1.11.2

这有效：

{% if n == "1" %}
    {{ n }}
{% endif %}

这不是：

{% if n=="1" %}
    {{ n }}
{% endif %}

回溯：

Internal Server Error: /form/
Traceback (most recent call last):
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/smartif.py", line 175, in translate_token
    op = OPERATORS[token]
KeyError: 'n=="1"'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/core/handlers/exception.py", line 41, in inner
    response = get_response(request)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/core/handlers/base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/views/generic/base.py", line 68, in view
    return self.dispatch(request, *args, **kwargs)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/views/generic/base.py", line 88, in dispatch
    return handler(request, *args, **kwargs)
  File "/home/michael/workspace/simple_project/home/views.py", line 22, in get
    {"n": n})
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/shortcuts.py", line 30, in render
    content = loader.render_to_string(template_name, context, request, using=using)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/loader.py", line 67, in render_to_string
    template = get_template(template_name, using=using)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/loader.py", line 21, in get_template
    return engine.get_template(template_name)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/backends/django.py", line 39, in get_template
    return Template(self.engine.get_template(template_name), self)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/engine.py", line 162, in get_template
    template, origin = self.find_template(template_name)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/engine.py", line 136, in find_template
    name, template_dirs=dirs, skip=skip,
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/loaders/base.py", line 44, in get_template
    contents, origin, origin.template_name, self.engine,
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 191, in __init__
    self.nodelist = self.compile_nodelist()
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 230, in compile_nodelist
    return parser.parse()
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 515, in parse
    raise self.error(token, e)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 513, in parse
    compiled_result = compile_func(self, token)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/loader_tags.py", line 312, in do_extends
    nodelist = parser.parse()
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 515, in parse
    raise self.error(token, e)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 513, in parse
    compiled_result = compile_func(self, token)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/loader_tags.py", line 255, in do_block
    nodelist = parser.parse(('endblock',))
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 515, in parse
    raise self.error(token, e)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 513, in parse
    compiled_result = compile_func(self, token)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/defaulttags.py", line 968, in do_if
    condition = TemplateIfParser(parser, bits).parse()
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/defaulttags.py", line 900, in __init__
    super(TemplateIfParser, self).__init__(*args, **kwargs)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/smartif.py", line 166, in __init__
    mapped_tokens.append(self.translate_token(token))
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/smartif.py", line 177, in translate_token
    return self.create_var(token)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/defaulttags.py", line 903, in create_var
    return TemplateLiteral(self.template_parser.compile_filter(value), value)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 600, in compile_filter
    return FilterExpression(token, self)
  File "/home/michael/workspace/venv/simple_project/lib/python3.5/site-packages/django/template/base.py", line 700, in __init__
    "from '%s'" % (token[upto:], token))
django.template.exceptions.TemplateSyntaxError: Could not parse the remainder: '=="1"' from 'n=="1"'
[22/Jun/2017 08:15:21] "GET /form/?n=1 HTTP/1.1" 500 200974

文档似乎对此保持沉默。我读过这个：https://docs.djangoproject.com/en/1.11/ref/templates/language/#tags https://docs.djangoproject.com/en/1.11/ref/templates/builtins/#operator

你能告诉我为什么这些空间很重要。我的意思是在Django中忽略其他空格。与{{var}}和{{var}}一样。

如果空格很重要，也许我们应该在文档中强调这一点？

Answer 1

这是因为模板标签和变量之间存在根本区别。模板标签接受需要用空格分隔的参数。在幕后，模板标签被解构，内容在每个空间上分开。某些模板标签可以接受不同数量的参数，但每个模板标签都有自己的实现方式。

你可以这样做（你留下第一个和最后一个空格）

{%if n == "1"%}

但不是这个

{% if n=="1" %}

因为在后一种情况下你只有一个参数。 if模板标签实际上只能接受1个参数，但它必须是一个布尔值：True或False。

if标签中= =运算符的空格

1 个答案: