Check if key exists in a Python dict in Jinja2 templates

Question

I have a python dictionary:

settings = {
   "foo" : "baz",
   "hello" : "world"
}

This variable settings is then available in the Jinja2 template.

I want to check if a key myProperty exists in the settings dict within my template, and if so take some action:

{% if settings.hasKey(myProperty) %}
   takeSomeAction();
{% endif %}

What is the equivalent of hasKey that I can use?

Solution 1

Like Mihai and karelv have noted, this works:

{% if 'blabla' in item %}
  ...
{% endif %}

I get a 'dict object' has no attribute 'blabla' if I use {% if item.blabla %} and item does not contain a blabla key

Solution 2

You can test for key definition this way:

{% if settings.property is defined %}

#...
{% endif %}

Solution 3

This works fine doesn't work in cases involving dictionaries. In those cases, please see the answer by tshalif. Otherwise, with SaltStack (for example), you will get this error:

Unable to manage file: Jinja variable 'dict object' has no attribute '[attributeName]'

if you use this approach:

{% if settings.myProperty %}

note:
Will also skip, if settings.myProperty exists, but is evaluated as False (e.g. settings.myProperty = 0).

Comments

[Amal Antony]

Can myProperty be a variable in the approach above?

[Mihai Zamfir]

Yes, a key in a dictionary. Is the equivalent of hasKey. And btw, hasKey is deprecated. Use in instead

[karelv]

when setting.myProperty exists, but it is equal to zero (integer 0) or to the boolean value False, this if test not for 'hasKey'. This means you need: {% if 'myProperty' in settings %}

[ryantuck]

this doesn't work for me (at least working with ansible). i found i needed {% if settings.myProperty is defined %}.

[chesterbr]

Same for me. In my particular case I'm using Jinja2 inside Ansible.

[Florian Neumann]

I don't get why this is accepted as answer - it throws an error if the dict is missing the key. Please correct the answer.

[Florian Neumann]

@MihaiZamfir There is no reason to interpret my commentary with excessive emotion. tshalif prooved the failure - and his answer seems to be the more robust one and even if "the" answer is right for a subset of use cases, it should in my opinion at least reflect that it might not fit for all use cases.

[Edward Fung]

Looks like this answer fails if settings.myProperty is an empty dictionary/list.

[Drew]

Using jinja2 inside Ansible. Nothing helps. Both {% if 'blabla' in item %} and {% if item.blabla %} return the same 'dict object' has no attribute 'blabla' wtf???

[Marc Tamsky]

Answer by @RyanTuck is the most correct and works regardless of the Boolean (True/False) status of myProperty :: {% if settings.myProperty is defined %}

[ma3oun]

fails when the key is not existent

[blkpingu]

argument of type 'StringField' is not iterable. Does not work for me

[Mayank Porwal]

This looks like the correct way of checking if a key is present in dict or not. +1

[Samha']

Your answer checks for object attributes, not dict keys.