Jinja2 template variable if None Object set a default value

Question

How to make a variable in jijna2 default to    if object is None instead of doing something like this            if p                  p User  first name              else            NONE         endif      So if object p is None I want to default the values of p  first name and last name  to     Basically   nvl p User first name          Error receiving   Error   jinja2 exceptions UndefinedError     UndefinedError   None  has no attribute  User

User · Answer

Following this doc you can do this that way      p User  first name   default  NONE

User · Answer

According to docs you can just do      p default     true       Cause None casts to False in boolean context     Update  As lindes mentioned  it works only for simple data types

User · Answer

As another solution  kind of similar to some previous ones         p is defined and p User is defined and p User  first name      default  NONE   True       Note the last variable  p User  first name    does not have the if defined test after it

User · Answer

I usually define an nvl function  and put it in globals and filters   def nvl  args       for item in args          if item is not None              return item     return None  app jinja env globals  nvl     nvl app jinja env filters  nvl     nvl   Usage in a template    lt span gt Welcome    nvl person nick  person name   Anonymous      lt span gt      or    lt span gt Welcome    person nick   nvl person name   Anonymous      lt span gt

User · Answer

p User  first name   or  My default string

User · Answer

To avoid throw a exception while  p  or  p User  is None  you can use       p and p User and p User  first name    or  default value

User · Answer

As of Ansible 2 8  you can just use      p User  first name        See https   docs ansible com ansible latest porting guides porting guide 2 8 html jinja-undefined-values

User · Answer

As addition to other answers  one can write something else if variable is None like this      variable or

User · Answer

Use the none test  not to be confused with Python s None object       if p is not none              p User  first name         else        NONE    endif     or     p User  first name   if p is not none else  NONE      or if you need an empty string     p User  first name   if p is not none

User · Answer

You can simply add  quot default none quot  to your variable as the form below mentioned     your var   default  NONE   boolean true

[jinja2] Jinja2 template variable if None Object set a default value

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