未定义变量:如果模板中引用了未定义的变量,Jinja2会抛出一个异常。为了避免这种情况,可以使用 {{ variable if variable is defined else 'default_value' }} 来提供一个默认值。 希望这些信息能帮助你更好地理解如何在Jinja2中定义和使用变量。如果有任何其他问题,请随时问我!
或者在jinja2中,您可以首先检查是否定义了变量。{% if variable is defined %},因此在模板word_count.html中,循环应该由if条件包装。 {% if results is defined %} {% for key, value in results.items() %} {{ key }} {{ value }} {% endfor %} {% endif %} (查看英文版本获取更加准确...
callable(object) Return whether the object is callable (i.e., some kind of function). Note that classes are callable, as are instances with a __call__() method. defined(value) Return true if the variable is defined: {%ifvariableisdefined%}value of variable:{{variable}}{%else%}variable...
{%ifloop.indexisdivisibleby3%}{%ifloop.indexisdivisibleby(3)%} 常见的测试函数有: callable(object)是否是一个函数, defined(value) 值是否定义,iterable(value)是否可迭代,lower(value)是否小写,none(value)是否为none,number(value)是否是数字 string(value)是否是字符串 {%ifvariableisdefined%}value of ...
The if statement in Jinja is comparable with the Python if statement. In the simplest form, you can use it to test if a variable is defined, not empty and not false: {% if users %} {% for user in users %} {{ user.username|e }} {% endfor %} ...
This will output the value of my_variable if the variable was defined, otherwise 'my_variable is not defined'. If you want to use default with variables that evaluate to false you have to set the second parameter to true: {{ ''|default('the string was empty', true) }} Aliases : ...
{% if var != 0 %} Value is not 0 {% endif %} ```3.如何判断一个变量是否存在或非空？可以使用`is defined`来检查变量是否已经定义，`is not none`来检查变量是否为非空。例如：```{% if var is defined %} Variable exists {% endif %} {% if var is not none %} Variable is not ...
If The if statement in Jinja is comparable with the Python if statement. In the simplest form, you can use it to test if a variable is defined, not empty and not false: {% if users %} {% for user in users %} {{ user.username|e }} {% endfor %} ...
variable_start_string="${", variable_start_string="}", comment_start_string="<#--", comment_end_string="--#>", ...) 这样,我们的模板可以设计为下面的样子: <# block title #> Index <# endblock #> ${name} <#-- this is comment --#> ...
string(value):将变量转换成字符串。wordcount(s):计算一个长字符串中单词的个数。九:测试器测试器主要用来判断一个值是否满足某种类型,语法是:if...is...:{% if variable is escaped%}value of variable: {{ escaped }}{% else %}variable is not escaped{% endif %}Jinja2中测试器有:callab...