1、变量标签：{{变量}}
<html><body>{{ now }}</body></html>
2、for循环标签：{% for item in list %}，{% endfor %}
<ul>
{% for item in list %}
<li>{{ item }}</li>
{% endfor %}
</ul>
3、if-else分支标签：｛% If %｝，｛% else %｝，｛% endif %｝
{% if true %}
<p> it is atrue part.</p>
{% else %}
<p> it is a false part.</p>
{% endif %}