app_template_filter with multiple arguments

Question

How can I pass two arguments to app_template_filter (doc)? This works well if I use only one argument. But in this case, I need two.

@mod.app_template_filter('posts_page')
def posts(post_id, company_id):
    pass

{{ post.id, post.company.id | posts_page }}

Error:

TypeError: posts_page() takes exactly 2 arguments (1 given)

Asked By: user455318

||

Source

Answer 1

From the Jinja docs,

Variables can be modified by filters. Filters are separated from the variable by a pipe symbol (|) and may have optional arguments in parentheses. Multiple filters can be chained. The output of one filter is applied to the next.

Filters are designed to modify one variable at a time. You’re looking for a context processor:

Variables are not limited to values; a context processor can also make functions available to templates (since Python allows passing around functions)

For example,

@app.context_processor
def add():
    def _add(int1, int2):
        return int(int1) + int(int2)
    return dict(add=_add)

can be used in the template as

{{ add(a, b) }}

You can adopt this as your posts_page method:

@app.context_processor
def posts_page():
    def _posts_page(post_id, company_id):
        # ...
        return value
    return dict(posts_page=_posts_page)

Answered By: Celeo

Answer 2

While you may use a context processor, it may not always be what you want.

The docs snippet in the accepted answer says:

[Filters] may have optional arguments in parentheses.

So, looking at the asker’s template filter:

@mod.app_template_filter('posts_page')
def posts(post_id, company_id):
    pass

The following is valid in the template:

{{ post.id|posts_page(post.company_id) }}

Answered By: multithr3at3d

Answer 3

This is how I do it, but the purists might not like it, it might not be "pythonistic" given the "modify one variable" thing. However, I realize that modifying one variable might required input from several values.

Template:

{% set args = { 'post_id': post.id, 'company_id': post.company.id } %}
...
{{ args | posts_page }}

Server:

@mod.app_template_filter('posts_page')
def posts(args):
    post_id    = args['post_id']
    company_id = args['company_id']

Answered By: user3481644

app_template_filter with multiple arguments

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