template blocks start or end with "{%-" or "-%}" symbols

Question

I'm reading "flask_bootstrap/templates/bootstrap/base.html" on GitHub, and find some block symbols strange, like {%- block ... %} or {% endblock ... -%}. Why there is "-" before or after {% or %}?

Will it make the block declaration different than the normal? I'm going to extend this file, so I'd like to know in detail.

They're used to [control whitespace](http://jinja.pocoo.org/docs/dev/templates/#whitespace-control). — dirn, Sep 25 '16 at 05:39

score 1 · Accepted Answer · answered Sep 25 '16 at 05:37

1

That particular feature (whitespace control) is not from the Flask server, but from Jinja2 template engine.

From the linked docs:

You can also strip whitespace in templates by hand. If you add a minus sign (-) to the start or end of a block (e.g. a For tag), a comment, or a variable expression, the whitespaces before or after that block will be removed:
{% for item in seq -%}
    {{ item }}
{%- endfor %}

answered Sep 25 '16 at 05:37

hjpotter92

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Thanks for the doc link, hjpotter92! I didn't find it by google. Good to know that sign (-) does have a purpose. – ping Sep 25 '16 at 17:36

template blocks start or end with "{%-" or "-%}" symbols

1 Answers1