Partially render in Jinja
source link: https://www.chunyangwen.com/blog/python/jinja-partial-template.html
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Partially render in Jinja
Posted by chunyang on June 7, 2022A Jinja template can be rendered. Sometimes the data we need can not be collected in just one place. It will be helpful if we can render a template multiple times.
By default, a Jinja template can not be rendered multiple times. It will raise an exception or insert null values into the corresponding placeholders.
In the blog, we will use a trick to mimic the partially rendering behavior. Jinja has an
operator raw which can be used to render its original content.
from jinja2 import Template
template_str = """
{% raw %} {% raw %}
{{hi}}
{% endraw %}
"""
partial_template_str = Template(template_str).render()
result = Template(partial_template_str).render(hi=3)
But using raw will introduce redundant newlines. We can not use - to remove the spaces.
It is wrong sometimes we remove the leading spaces.
from jinja2 import Template
template_str = """
{% raw %}
{{hi}}
{% endraw %}
"""
partial_template_str = Template(template_str, trim_blocks=True, lstrip_blocks=True).render()
result = Template(partial_template_str).render(hi=3)
print(result)
If the leading spaces are not meaningless to your program, you can use -
to remove them. Referecne
from jinja2 import Template
template_str = """
{% raw -%}
{{hi}}
{% endraw %}
"""
partial_template_str = Template(template_str, trim_blocks=True, lstrip_blocks=True).render()
result = Template(partial_template_str).render(hi=3)
print(result)
If we need more nested templates, such as we want a template to be rendered three or more times, the code will be ugly. It seems that Jinja does not provide way to implement a customized operator
from jinja2 import Template
template_str = """
{% raw -%}
{{hi}}
{% endraw -%}
{{'{%'}} raw {{'%}'}}
{{hello}}
{{'{%'}} endraw {{'%}'}}
"""
partial_template_str = Template(template_str, trim_blocks=True, lstrip_blocks=True).render()
print(partial_template_str)
print("=" * 10)
result = Template(partial_template_str).render(hi=3)
print(result)
print("=" * 10)
final_result = Template(result).render(hello=4)
print(final_result)
raw and endraw can not be nested. You are not allowed to insert raw and
endraw block in another raw and endraw block`.
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