Get lengths of a list in a jinja2 template
Question:
How do I get the number of elements in a list in jinja2 template?
For example, in Python:
print(template.render(products=[???]))
and in jinja2
<span>You have {{what goes here?}} products</span>
Answers:
<span>You have {{products|length}} products</span>
You can also use this syntax in expressions like
{% if products|length > 1 %}
jinja2’s builtin filters are documented here; and specifically, as you’ve already found, length (and its synonym count) is documented to:
Return the number of items of a sequence or mapping.
So, again as you’ve found, {{products|count}} (or equivalently {{products|length}}) in your template will give the “number of products” (“length of list”)
Alex’ comment looks good but I was still confused with using range.
The following worked for me while working on a for condition using length within range.
{% for i in range(0,(nums['list_users_response']['list_users_result']['users'])| length) %}
<li> {{ nums['list_users_response']['list_users_result']['users'][i]['user_name'] }} </li>
{% endfor %}
I’ve experienced a problem with length of None, which leads to Internal Server Error: TypeError: object of type ‘NoneType’ has no len()
My workaround is just displaying 0 if object is None and calculate length of other types, like list in my case:
{{'0' if linked_contacts == None else linked_contacts|length}}
If for loop with array is used then you can use the following
{% for i in range(array|length) %}
array[i]
{% endfor %}
How do I get the number of elements in a list in jinja2 template?
For example, in Python:
print(template.render(products=[???]))
and in jinja2
<span>You have {{what goes here?}} products</span>
<span>You have {{products|length}} products</span>
You can also use this syntax in expressions like
{% if products|length > 1 %}
jinja2’s builtin filters are documented here; and specifically, as you’ve already found, length (and its synonym count) is documented to:
Return the number of items of a sequence or mapping.
So, again as you’ve found, {{products|count}} (or equivalently {{products|length}}) in your template will give the “number of products” (“length of list”)
Alex’ comment looks good but I was still confused with using range.
The following worked for me while working on a for condition using length within range.
{% for i in range(0,(nums['list_users_response']['list_users_result']['users'])| length) %}
<li> {{ nums['list_users_response']['list_users_result']['users'][i]['user_name'] }} </li>
{% endfor %}
I’ve experienced a problem with length of None, which leads to Internal Server Error: TypeError: object of type ‘NoneType’ has no len()
My workaround is just displaying 0 if object is None and calculate length of other types, like list in my case:
{{'0' if linked_contacts == None else linked_contacts|length}}
If for loop with array is used then you can use the following
{% for i in range(array|length) %}
array[i]
{% endfor %}