old_contents: #!/usr/bin/env python
  
  if __name__ == '__main__':
      import os
      import sys
      if not os.path.exists('.tox/configure'):
          import virtualenv
          import subprocess
          print("Bootstrapping ...")
          virtualenv.create_environment('.tox/configure')
          print("Installing `jinja2` and `matrix` into bootstrap environment ...")
          if sys.platform == 'win32':
              subprocess.check_call([r'.tox\configure\Scripts\pip', 'install', 'jinja2', 'matrix'])
          else:
              subprocess.check_call(['.tox/configure/bin/pip', 'install', 'jinja2', 'matrix'])
      if sys.platform == 'win32':
          exec(compile(
              open(r'.tox\configure\Scripts\activate_this.py').read(),
              r'.tox\configure\Scripts\activate_this.py',
              'exec'
          ), dict(__file__=r'.tox\configure\Scripts\activate_this.py'))
      else:
          exec(compile(
              open('.tox/configure/bin/activate_this.py').read(),
              '.tox/configure/bin/activate_this.py',
              'exec'
          ), dict(__file__='.tox/configure/bin/activate_this.py'))
      import jinja2
      import matrix
  
      jinja = jinja2.Environment(
          loader=jinja2.FileSystemLoader(os.path.join('ci', 'templates')),
          trim_blocks=True,
          lstrip_blocks=True,
          keep_trailing_newline=True
      )
      tox_environments = {}
      for alias, conf in matrix.from_file('setup.cfg').items():
          python = conf['python_versions']
          deps = conf['dependencies']
          cover = {'false': False, 'true': True}[conf['coverage_flags'].lower()]
          env_vars = conf['environment_variables']
  
          tox_environments[alias] = {
              'python': 'python' + python if 'py' not in python else python,
              'deps': deps.split(),
              'cover': cover,
              'env_vars': env_vars.split(),
          }
  
      for name in os.listdir(os.path.join('ci', 'templates')):
          with open(name, 'w') as fh:
              fh.write(jinja.get_template(name).render(tox_environments=tox_environments))
          print("Wrote %s" % name)
  
      print("DONE.")
  
new_contents: #!/usr/bin/env python
  
  if __name__ == '__main__':
      import os
      import sys
      if not os.path.exists('.tox/configure'):
          import subprocess
          print("Bootstrapping ...")
          subprocess.check_call(['python', '-mvirtualenv', '.tox/configure'])
          print("Installing `jinja2` and `matrix` into bootstrap environment ...")
          if sys.platform == 'win32':
              subprocess.check_call([r'.tox\configure\Scripts\pip', 'install', 'jinja2', 'matrix'])
          else:
              subprocess.check_call(['.tox/configure/bin/pip', 'install', 'jinja2', 'matrix'])
      if sys.platform == 'win32':
          exec(compile(
              open(r'.tox\configure\Scripts\activate_this.py').read(),
              r'.tox\configure\Scripts\activate_this.py',
              'exec'
          ), dict(__file__=r'.tox\configure\Scripts\activate_this.py'))
      else:
          exec(compile(
              open('.tox/configure/bin/activate_this.py').read(),
              '.tox/configure/bin/activate_this.py',
              'exec'
          ), dict(__file__='.tox/configure/bin/activate_this.py'))
      import jinja2
      import matrix
  
      jinja = jinja2.Environment(
          loader=jinja2.FileSystemLoader(os.path.join('ci', 'templates')),
          trim_blocks=True,
          lstrip_blocks=True,
          keep_trailing_newline=True
      )
      tox_environments = {}
      for alias, conf in matrix.from_file('setup.cfg').items():
          python = conf['python_versions']
          deps = conf['dependencies']
          cover = {'false': False, 'true': True}[conf['coverage_flags'].lower()]
          env_vars = conf['environment_variables']
  
          tox_environments[alias] = {
              'python': 'python' + python if 'py' not in python else python,
              'deps': deps.split(),
              'cover': cover,
              'env_vars': env_vars.split(),
          }
  
      for name in os.listdir(os.path.join('ci', 'templates')):
          with open(name, 'w') as fh:
              fh.write(jinja.get_template(name).render(tox_environments=tox_environments))
          print("Wrote %s" % name)
  
      print("DONE.")
  
subject: Update from template.