Check if key exists in a dict in Jinja2 template on ansible

Question:

I have a host_var in ansible with dict with all interfaces:

---
interfaces:
  vlan0:
    ip: 127.0.0.1
    mask: 255.255.255.0
    state: true

  vlan2:
    ip: 127.0.1.1
    mask: 255.255.255.0
    state: true

---

interfaces:

vlan0:

ip: 127.0.0.1

mask: 255.255.255.0

state: true

vlan2:

ip: 127.0.1.1

mask: 255.255.255.0

state: true

And I want to check if dict has a key vlan1 if ok put to template value vlan1.ip else put vlan2.ip.

{% if interfaces.vlan1 %} 
# and also I try {% if 'vlan1' in interfaces %}
{{ interfaces.vlan1.ip }};
{% else %}
{{ interfaces.vlan2.ip|default("127.0.0.1") }};
{% endif %};

{% if interfaces.vlan1 %}

# and also I try {% if 'vlan1' in interfaces %}

{{ interfaces.vlan1.ip }};

{% else %}

{{ interfaces.vlan2.ip|default("127.0.0.1") }};

{% endif %};

But i have an error:

fatal: [127.0.0.1] => {'msg': "AnsibleUndefinedVariable: One or more undefined variables: 'dict object' has no attribute 'vlan1'", 'failed': True}

1 2	fatal: [127.0.0.1] => {'msg': "AnsibleUndefinedVariable: One or more undefined variables: 'dict object' has no attribute 'vlan1'", 'failed': True}

I found that it have to re work in Jinja2 but it seems to doesn’t work in ansible. Maybe someone have another way for solving this problem?
When I define vlan1 it works fine. Ansible version 1.9.2

I was trying to reproduce it in python and have no error if my dictionary have not key vlan1. thanks to @GUIDO

>>> from jinja2 import Template
>>> b = Template("""
... {% if interfaces.vlan1 %}
... {{ interfaces.vlan1.ip }}
... {% else %}
... {{ interfaces.vlan2.ip|default("127.0.3.1") }}
... {% endif %}""")
>>> b.render(interfaces={'vlan3':{'ip':'127.0.1.1'},'vlan2':{'ip':'127.0.2.1'}})
u'\n\n127.0.2.1\n'
>>> b.render(interfaces={'vlan1':{'ip':'127.0.1.1'},'vlan2':{'ip':'127.0.2.1'}})
u'\n\n127.0.1.1\n'

>>> from jinja2 import Template

>>> b = Template("""

... {% if interfaces.vlan1 %}

... {{ interfaces.vlan1.ip }}

... {% else %}

... {{ interfaces.vlan2.ip|default("127.0.3.1") }}

... {% endif %}""")

>>> b.render(interfaces={'vlan3':{'ip':'127.0.1.1'},'vlan2':{'ip':'127.0.2.1'}})

u'\n\n127.0.2.1\n'

>>> b.render(interfaces={'vlan1':{'ip':'127.0.1.1'},'vlan2':{'ip':'127.0.2.1'}})

u'\n\n127.0.1.1\n'

Answer:

The answer is simple and it showed on ansible error message. First of all I need to check if var is defined.

{% if interfaces.vlan1 is defined %}
{{ interfaces.vlan1.ip }}
{% else %}
{{ interfaces.vlan2.ip|default("127.0.3.1") }}
{% endif %}

{% if interfaces.vlan1 is defined %}

{% else %}

{% endif %}

This combination works well.

Question:

Answer:

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