for
Loop over each item in a sequence or a mapping. For example, to display a list
of users provided in a variable called users:
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<h1>Members</h1>
<ul>
{% for user in users %}
<li>{{ user.username|e }}</li>
{% endfor %}
</ul>Note
A sequence or a mapping can be either an array or an object implementing
the Traversable interface.
If you do need to iterate over a sequence of numbers, you can use the ..
operator:
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{% for i in 0..10 %}
* {{ i }}
{% endfor %}The above snippet of code would print all numbers from 0 to 10.
It can be also useful with letters:
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{% for letter in 'a'..'z' %}
* {{ letter }}
{% endfor %}The .. operator can take any expression at both sides:
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{% for letter in 'a'|upper..'z'|upper %}
* {{ letter }}
{% endfor %}Tip
If you need a step different from 1, you can use the range function
instead.
The loop variable
Inside of a for loop block you can access some special variables:
| Variable | Description |
|---|---|
loop.index |
The current iteration of the loop. (1 indexed) |
loop.index0 |
The current iteration of the loop. (0 indexed) |
loop.revindex |
The number of iterations from the end of the loop (1 indexed) |
loop.revindex0 |
The number of iterations from the end of the loop (0 indexed) |
loop.first |
True if first iteration |
loop.last |
True if last iteration |
loop.length |
The number of items in the sequence |
loop.parent |
The parent context |
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{% for user in users %}
{{ loop.index }} - {{ user.username }}
{% endfor %}Note
The loop.length, loop.revindex, loop.revindex0, and
loop.last variables are only available for PHP arrays, or objects that
implement the Countable interface.
The loop.parent variable gives access to the context enclosing the for
loop. It is not limited to nested loops: it exposes the whole context as it was
before the loop started, which covers two common needs.
When loops are nested, the parent context holds the outer loop variable, so
the inner loop can reach the outer iteration state:
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{% for topic, messages in topics %}
* {{ loop.index }} : {{ topic }}
{% for message in messages %}
- {{ loop.parent.loop.index }}.{{ loop.index }}: {{ message }}
{% endfor %}
{% endfor %}Here loop.parent.loop.index is the index of the current topic from the
outer for loop.
loop.parent also lets you reach a variable that the loop variable shadows:
when both share the same name, the outer value is still available through the
parent context:
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{% set user = 'Fabien' %}
{% for user in ['Homer', 'Bart'] %}
{{ loop.index }}. {{ user }} (outer user: {{ loop.parent.user }})
{% endfor %}This outputs 1. Homer (outer user: Fabien) then 2. Bart (outer user: Fabien).
See also the recipe on accessing the parent context in nested loops.
The else Clause
If no iteration took place because the sequence was empty, you can render a
replacement block by using else:
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<ul>
{% for user in users %}
<li>{{ user.username|e }}</li>
{% else %}
<li><em>no user found</em></li>
{% endfor %}
</ul>Iterating over Keys
By default, a loop iterates over the values of the sequence. You can iterate
on keys by using the keys filter:
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<h1>Members</h1>
<ul>
{% for key in users|keys %}
<li>{{ key }}</li>
{% endfor %}
</ul>Iterating over Keys and Values
You can also access both keys and values:
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<h1>Members</h1>
<ul>
{% for key, user in users %}
<li>{{ key }}: {{ user.username|e }}</li>
{% endfor %}
</ul>Iterating over a Subset
You might want to iterate over a subset of values. This can be achieved using the slice filter:
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<h1>Top Ten Members</h1>
<ul>
{% for user in users|slice(0, 10) %}
<li>{{ user.username|e }}</li>
{% endfor %}
</ul>Iterating over a String
To iterate over the characters of a string, use the split filter:
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<h1>Characters</h1>
<ul>
{% for char in "諺 / ことわざ"|split('') -%}
<li>{{ char }}</li>
{%- endfor %}
</ul>