14-C03P05

C03P05 - Simple template engine

We are working on a piece of software that needs a simple templating engine, so we can send simple templated emails.

In a module called template.py implement the following class:

class TemplateEngine:
    def __init__(self, template):
        pass

    def render(self, **context):
        """
        Renders `self.template` by interpolating the variables with data from `context`.

        Raise `TemplatEngineError` if not all variables, present in `self.template`, have values in `context`.
        """

    def extract_variables(self):
        """
        Returns a list of all variables names, that are present in `self.template`
        """

The class should behave as follows:

template = "Hello there, {{ x }}"
engine = TemplateEngine(template)

rendered = engine.render(x="general Kenobi.")
print(rendered)  # "Hello there, general Kenobi."

variables = engine.extract_variables()
print(variables)  # ["x"]

Few important things:

1. The engine should support multiline strings.
2. All of those are valid: {{x}}, {{ x}}, {{ x }}, {{ x}}, etc. You can have arbitrary whitespace between {{, the variable name and }}.
3. One variable can occur in multiple places in the template.
4. Behavior of the render method is described in the docstring.
5. In order to show that your implementation is working as expected, cover the TemplateEngine implementation with tests, placed in template_tests.py

Few more examples

template = """
Hello {{ first_name }} {{ last_name }},

I hope this email finds you well.

We are currently running a promotion for {{ product }}.

You can get your discount {{ here }}
"""

engine = TemplateEngine(template)

variables = engine.extract_variables()
print(variables)  # ["first_name", "last_name", "product", "here"]

rendered = engine.render(
  first_name="Ivan",
  last_name="Ivanov",
  product="Python course",
  here="https://hackbulgaria.com/python-101-forever"
)
print(rendered)

The rendered version should look like this:

Hello Ivan Ivanov,

I hope this email finds you well.

We are currently running a promotion for Python course.

You can get your discount https://hackbulgaria.com/python-101-forever