Write a Python script that reads in a phrase, calculates the average word length in that phrase, and then displays the result.

As an example, the phrase "Thirty days hath September" has an average word length of 5.75 characters, and the phrase "All the rest have thirty-one" has an average word length of 4.8 characters.

• Prompt the user for the name of an input file and an output file
• Open the input file for reading, and open the output file for writing
• Use readlines.
• For each line in the input file:
  • Compute the average word length for the line
  • Write to the output file: the line number, followed by a single space, followed by a colon (:) and a single space, followed by the average word length
  • When done, close both the input and output files