Jinja: Confusing error w/ Python 3 and templates that use iteritems()

Created on 27 Sep 2012 · 5Comments · Source: pallets/jinja

Consider:

#!/usr/bin/env python3

from collections import OrderedDict

import jinja2

t = '''
{% for key, value in d.iteritems() %}
* {{ key }}: {{ value }}
{% endfor %}
'''

jt = jinja2.Template(t)

d = OrderedDict()
d['one'] = 1
d['two'] = 2
d['three'] = 3

print(jt.render(d=d))

When run w/ Python 3, you get an confusing exception:

Traceback (most recent call last):
  File "jinja2-OrderedDict.py", line 20, in <module>
    print(jt.render(d=d))
  File "/usr/lib/python3/dist-packages/jinja2/environment.py", line 895, in render
    return self.environment.handle_exception(exc_info, True)
  File "/usr/lib/python3/dist-packages/jinja2/environment.py", line 671, in handle_exception
    raise exc_value.with_traceback(tb)
  File "<template>", line 2, in <module>
jinja2.exceptions.UndefinedError: b"'collections.OrderedDict object' has no attribute 'iteritems'"

This is because the template uses iteritems, which is removed in Python 3. From the above exception, it's not clear the problem is in the template—it should be.

It works for normal Python 3 dictionaries because lines 205–210 of Jinja2 v2.61 add back an iteritems method:

    # not available on python 3
    if hasattr(dict, 'iterkeys'):
        iterkeys = _all('iterkeys')
        itervalues = _all('itervalues')
        iteritems = _all('iteritems')
    del _all

What's the best way to fix this? Better detect dict-like objects, try to spit out a better error, etc?

Source

samatjain

Most helpful comment

Dictionaries do not have iteritem methods in 3.x. You will need to change to .items(). Nothing I can do about that.

mitsuhiko on 20 May 2013

👍37 ❤7

All 5 comments

Dictionaries do not have iteritem methods in 3.x. You will need to change to .items(). Nothing I can do about that.

mitsuhiko on 20 May 2013

👍37 ❤7

It would be nice if there were a built-in filter for this and other python 2to3 oddities.

wryfi on 20 Mar 2017

Unless you have huge dicts, using .items() is not /that/ bad

ThiefMaster on 20 Mar 2017

Here's a way to get around it:

import six

env = jinja2.Environment(loader=jinja2.FileSystemLoader('your_dir'))
env.globals['six_iteritems'] = six.iteritems
template = env.get_template('your_template')

Then in your template:

use:
{% for key, value in six_iteritems(your var) %}

It's kinda ugly, but it does work.