CODEWITHSUNDEEP
jinja2
ElBel
ElBel

Reputation: 1994

jinja2 string comparison when one value is null?

Jinja2 template code:

{% if u.user_name == u.user_email %}
 {{ u.user_email }}
{% else %}
 {{ u.user_name }}<br />
 {{ u.user_email }}
{% endif %}

Usually the data source sets the user_name field to user_email if there is no separate name. However, sometimes there is nothing defined for the user_name field at all.

The problem is that in the Jinja2 code above, if the user_name field is undefined / null, the test above evaluates to false and both lines get spit out — one of which is blank.

I'm not sure how to properly write this test syntax. I've read the documentation and have tried approaches like Convert integer to string Jinja and compare two variables in jinja2 template. I guess I have a problem with data types, I'm just not sure how to write this syntax so that it works.

Any help is appreciated!

Upvotes: 5

Views: 21821

Answers (2)

WetroLam
WetroLam

Reputation: 21

There are these options for u.username:

  • u.user_name is not defined
  • u.user_name is None
  • u.user_name is an empty string
  • u.user_name is a non-empty string
{% if u.user_name is not defined or u.user_name == None  or u.user_name == '' or u.user_name == u.user_email %}
    {{ u.user_email }}
{% else %}
    {{ u.user_name }} <br />
    {{ u.user_email }}
{% endif %}

But a shorter solution is to use default filter:

{% if u.user_name | default(u.user_email, true) == u.user_email %}
    {{ u.user_email }}
{% else %}
    {{ u.user_name }} <br />
    {{ u.user_email }}
{% endif %}

If u.user_name is not defined, default filter returns its first argument (a default value), otherwise it returns u.user_name.

It is important to set the second argument of default to true. In that case default returns its first argument (the default value) for u.user_name defined as None or as an empty string.

docs: is , defined , default

Upvotes: 2

Andrew Kloos
Andrew Kloos

Reputation: 4598

You want is None... try this

{% if (u.user_name == None or u.user_name == '') and u.user_name == u.user_email %}
    {{ u.user_email }}
{% else %}
    {{ u.user_name }}<br />
    {{ u.user_email }}
{% endif %}

Hope this helps!

Upvotes: 8

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