Call a python function from jinja2

Question

I am using jinja2  and I want to call a python function as a helper  using a similar syntax as if I were calling a macro  jinja2 seems intent on preventing me from making a function call  and insists I repeat myself by copying the function into a template as a macro       Is there any straightforward way to do this   And  is there any way to import a whole set of python functions and have them accessible from jinja2  without going through a whole lot of rigamarole  such as writing an extension

User · Answer

I think jinja deliberately makes it difficult to run 'arbitrary' python within a template. It tries to enforce the opinion that less logic in templates is a good thing.

You can manipulate the global namespace within an Environment instance to add references to your functions. It must be done before you load any templates. For example:

from jinja2 import Environment, FileSystemLoader

def clever_function(a, b):
    return u''.join([b, a])

env = Environment(loader=FileSystemLoader('/path/to/templates'))
env.globals['clever_function'] = clever_function

User · Answer

I like  AJP s answer  I used it verbatim until I ended up with a lot of functions  Then I switched to a Python function decorator   from jinja2 import Template  template       Hi  my name is    custom function1 first name     My name is    custom function2 first name     My name is    custom function3 first name         jinga html template   Template template   def template function func       jinga html template globals func   name      func     return func   template function def custom function1 a       return a replace  o    ay     template function def custom function2 a       return a replace  o    ill     template function def custom function3 a       return  Slim Shady   fields     first name    Jo   print jinga html template render   fields     Good thing functions have a   name

User · Answer

John32323  s answer is a very clean solution  Here is the same one  but save into a seperate file  maybe more cleaner  Create helper file app helper py from app import app  def clever function 1        return u HELLO   def clever function 2 a  b       return a   b    app jinja env globals update      clever function 1 clever function 1      clever function 2 clever function 2     Import from app app py from app import routes from app import helper     add this one  Use like this app templates some html     clever function 1         clever function 2 a  b

User · Answer

Never saw such simple way at official docs or at stack overflow  but i was amazed when found this     jinja2   version      2 8 from jinja2 import Template  def calcName n  i       return     join  n    i   template   Template  Hello    calcName  Gandalf   2        template render calcName calcName    or template render   calcName   calcName

User · Answer

There s a much simpler decision   app route   x   def x        return render template  test html   foo y   def y text       return text  Then  in test html     foo  hi

User · Answer

Use a lambda to connect the template to your main code  return render template  clever template   clever function lambda x  clever function x    Then you can seamlessly call the function in the template    clever function value

User · Answer

To import all the builtin functions you can use   app jinja env globals update   builtins      Add    dict   after   builtins   if this doesn t work   Based on John32323 s answer

User · Answer

To call a python function from Jinja2  you can use custom filters which work similarly as the globals  http   jinja pocoo org docs dev api  writing-filters  It s quite simple and useful  In a file myTemplate txt  I wrote      data pythonFct      And in a python script   import jinja2  def pythonFct data       return  This is my data   0   format data   input  my custom filter works    loader   jinja2 FileSystemLoader path or       env   jinja2 Environment loader loader  env filters  pythonFct     pythonFct result   env get template  myTemplate txt   render data input  print result

User · Answer

For those using Flask  put this in your   init   py   def clever function        return u HELLO   app jinja env globals update clever function clever function    and in your template call it with    clever function

User · Answer

Note  This is Flask specific   I know this post is quite old  but there are better methods of doing this in the newer versions of Flask using context processors   Variables can easily be created    app context processor def example        return dict myexample  This is an example     The above can be used in a Jinja2 template with Flask like so      myexample       Which outputs This is an example   As well as full fledged functions    app context processor def utility processor        def format price amount  currency u                return u  0  2f  1   format amount  currency      return dict format price format price    The above when used like so      format price 0 33        Which outputs the input price with the currency symbol   Alternatively  you can use jinja filters  baked into Flask  E g  using decorators    app template filter  reverse   def reverse filter s       return s   -1    Or  without decorators  and manually registering the function   def reverse filter s       return s   -1  app jinja env filters  reverse     reverse filter   Filters applied with the above two methods can be used like this      for x in mylist   reverse       endfor

User · Answer

is there any way to import a whole set of python functions and have them accessible from jinja2    Yes there is  In addition to the other answers above  this works for me    Create a class and populate it with the associated methods e g  class Test jinja object       def   init   self           self myvar    sample var       def clever function  self           return  hello     Then create an instance of your class in your view function and pass the resultant object to your template as a parameter for the render template function  my obj   Test jinja object     Now in your template  you can call the class methods in jinja like so     my obj clever function

User · Answer

from jinja2 import Template  def custom function a       return a replace  o    ay    template   Template  Hey  my name is    custom function first name        func2 last name       template globals  custom function     custom function   You can also give the function in the fields as per Matroskin s answer  fields     first name    Jo    last name    Ko    func2   custom function  print template render   fields    Will output   Hey  my name is Jay Kay   Works with Jinja2 version 2 7 3  And if you want a decorator to ease defining functions on template globals check out Bruno Bronosky s answer

User · Answer

If you are doing it with Django  you can just pass the function with the context   context          title   My title        str   str        return render request   index html   context    Now you will be able to use the str function in jinja2 template

[python] Call a python function from jinja2

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