jinja-copy.py

# the expected result would be:
# {'configuration': {'index': 1, 'targets': {'index': 1}}}
# {'configuration': {'index': 2, 'targets': {'index': 2}}}
# the actual result is (see targets.index in 1st line):
# {'configuration': {'index': 1, 'targets': {'index': 2}}}
# {'configuration': {'index': 2, 'targets': {'index': 2}}}
from jinja2 import Environment
from jinja2.ext import do
env = Environment(extensions=[do])
template = env.from_string('''
{%- set template_config = {
  'index': none,
  'targets': {},
} %}

{%- set projects = {
  'foo': {},
  'bar': {},
} %}

{%- for project, projectdata in projects.items() %}
  {%- set config = template_config.copy() %}
  {%- do config.update({"index": loop.index}) %}
  {%- do config.targets.update({"index": loop.index}) %}

  {%- do projectdata.update({
    'configuration': config,
  }) %}
{%- endfor %}

{%- for project, projectdata in projects.items() %}
{{ projectdata }}
{%- endfor %}
''')
print(template.render())