Frame Hack Recipe: Ruby-Style String Interpolation

Step 2

Implement the interpolate function, using the getchunks function, which has been provided for you.

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

1. You will have to use the built-in eval function.
2. You should look closely at the return values of the getchunks function.
3. You need to differentiate between chunks that need to be eval’ed and the chunks that don’t need to be eval’ed.

Solution: solutions/interpolate2.py

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