Frame Hack Recipe: Ruby-Style String Interpolation
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Step 2
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Implement the ``interpolate`` function, using the ``getchunks`` function, which has been provided for you.

.. sourcecode:: python

    import sys, re
    from string import Template

    def getchunks(s):
        matches = list(re.finditer(r"\$\{(.*?)\}", s))

        if matches:
            pos = 0
            for match in matches:
                yield s[pos : match.start()]
                yield [match.group(1)]
                pos = match.end()
            yield s[pos:]

    def interpolate(templateStr):
        """Implement this function"""
        
    name = 'Guido van Rossum'
    places = 'Amsterdam', 'LA', 'New York', 'DC', 'Chicago',

    s = """My name is ${'Mr. ' + name + ', Esquire'}.

    I have visited the following cities:  ${', '.join(places)}.
    """

    print interpolate(s)
    
    
Expected output::

    My name is Mr. Guido van Rossum, Esquire.

    I have visited the following cities:  Amsterdam, LA, New York, DC, Chicago.
    
Hints:

.. class:: hintlist

#. You will have to use the built-in ``eval`` function.
#. You should look closely at the return values of the ``getchunks`` function.
#. You need to differentiate between chunks that need to be eval'ed and the chunks that don't need to be eval'ed.
    
Solution: `interpolate2.py <solutions/interpolate2.py>`_

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