Concatenate lists in JINJA2

How can I concatenate two list variables in jinja2?

E.G.

GRP1 = [1, 2, 3]
GRP2 = [4, 5, 6]

{# This works fine: #}
{% for M in GRP1 %}
    Value is {{M}}
{% endfor %}


{# But this does not: #}
{% for M in GRP1 + GRP2 %}
    Value is {{M}}
{% endfor %}

So, I have tried to concatenate the two lists using + (like you would in Python), but it turns out that they are not lists, but python xrange objects:

jijna2 error: unsupported operand type(s) for +: 'xrange' and 'xrange'

Is there a way for me to iterate over the concatenation of GRP1 and GRP2 in the same for loop?

Solution

AFAIK you can't do it using native Jinja2 templating. You're better off creating a new combined iterable and passing that to your template, eg:

from itertools import chain

x = xrange(3)
y = xrange(3, 7)
z = chain(x, y) # pass this to your template
for i in z:
    print i

As per comments, you can explicitly convert the iterables into lists, and concatenate those:

{% for M in GRP1|list + GRP2|list %}