Printing variables in Python 3.4

The syntax has changed in that print is now a function. This means that the % formatting needs to be done inside the parenthesis:¹

print("%d. %s appears %d times." % (i, key, wordBank[key]))

However, since you are using Python 3.x., you should actually be using the newer str.format method:

print("{}. {} appears {} times.".format(i, key, wordBank[key]))

Though % formatting is not officially deprecated (yet), it is discouraged in favor of str.format and will most likely be removed from the language in a coming version (Python 4 maybe?).

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_{¹Just a minor note: %d is the format specifier for integers, not %s.}