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Problem : Join two datasets

You are given two files, each containing various measurements $($one measurement per line$).$ For instance, these measurements could represent the population of different cities $($file #$1)$ and their corresponding area in square miles $($file #$2).$ Each measurement line begins with an item label $($the city name$),$ followed by a comma, and the measurement value. The measurements are not in any specific order.

For example, file #$1$ could have the following lines:

DC$,213280$

MD$,1198747$

VA$,239545$

While file #$2$ these other lines:

MD$,112.49$

VA$,412\mathrm{.}34$

DC$,31\mathrm{.}43$

Your task is to join the two files and produce a third set of measurements $($in this example, it could be the population per square mile$).$ All new measurements should be rounded to two decimal places.

Your program should take three parameters : two filenames, and a string specifying the operation to perform. The acceptable operation options are "sum", "subtract", "multiply", or "divide" $($in this instance, the operation to use would be "divide"$).$ It should return a dictionary containing the new set of measurements, where each dictionary entry maps the item's label $($key$)$ to its new measurement $($value$).$

Finally, your program must print the following message:

Created XX measurements with operation ZZZZ

where $ZZZZ$ is one of the four options above.