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Loop variables in custom python contextfunction #768

captainmalloc opened this issue Sep 8, 2017 · 1 comment · Fixed by #1242

Loop variables in custom python contextfunction #768

captainmalloc opened this issue Sep 8, 2017 · 1 comment · Fixed by #1242


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I am experiencing an unexpected behavior with Jinja and local variables in a for loop when accessing them from a custom Python context function.

Expected Behavior

I expected for every variable to be available in the context object in a python @contextfunction, even if it is defined/updated in a for loop.

Actual Behavior

The actual behavior is that only variables defined/updated outside the loop are available/have the expected value.

Template Code

Here is a simple template code to demonstrate the behavior:

>>> import jinja2
>>> jinja2.__version__
>>> @jinja2.contextfunction
... def myContextFunction(ctx):
...     return "myContextFunction: ctx['myI'] = " + str(ctx['myI'])
>>> tmplt = """
... {% for i in range(2): %}
... {%- set  myI = i -%}
...     {{ myContextFunction() }}
...     In template myI = {{ myI }}
... {% endfor %}
... """
>>> template = jinja2.Template(tmplt)
>>> template.globals['myContextFunction'] = myContextFunction
>>> template.render()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/arm/tools/python/jinja2_py2.7.8/2.9.4/rhe6-x86_64/lib/jinja2/", line 1008, in render
    return self.environment.handle_exception(exc_info, True)
  File "/arm/tools/python/jinja2_py2.7.8/2.9.4/rhe6-x86_64/lib/jinja2/", line 780, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "<template>", line 4, in top-level template code
  File "<stdin>", line 3, in myContextFunction
  File "/arm/tools/python/jinja2_py2.7.8/2.9.4/rhe6-x86_64/lib/jinja2/", line 253, in __getitem__
    raise KeyError(key)
KeyError: 'myI'
>>> context = {'myI' : 0}
>>> print template.render(**context)

myContextFunction: ctx['myI'] = 0
        In template myI = 0
myContextFunction: ctx['myI'] = 0
        In template myI = 1

My first goal was to access the i counter, or also the loop.index from my custom contextfunction. Also those variable, I expected to be defined in context, where not available.

Your Environment

  • Python version: Python 2.7.8
  • Jinja version: '2.9.4'
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pannal commented Sep 22, 2017

I have a similar problem. Not with looping the variable but simply with accessing the variable set in the template inside the contextfunction's passed context.

@pallets pallets deleted a comment from EpicWink May 23, 2020
@davidism davidism added this to the 3.0.0 milestone Mar 26, 2021
@github-actions github-actions bot locked as resolved and limited conversation to collaborators Apr 10, 2021
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3 participants