$1.$ Cyphertext: Encode and Decode

$1\mathrm{.}1$ Recall that in Practice Exercises you implemented a cypher text generator, which encrypts a

string by switching every letter at alphabetical position i with the uppercase letter at alphabetical

position $25-$i$.$

In this assignment, you are asked to reimplement it using a function:

Function: cypher$($s$)$

Input: s$,$ a string object

Return: the cypher text corresponding to s

Save the file in ps$01\_01.$py$.$ Test your function by passing it with a meaningful sentence.

Test your function again by passing the string returned by the function from the previous test.

Did you notice that the function can encode as well as decode? Explain why. Use your program

to decode the following: VEVIBLMV HSLFOW GZPV NRHG$\mathrm{.}6150!$ What does it say?

$1\mathrm{.}2$ You notice that digits are not encrypted. Improve your program so that any digit at position i

in digits $0-9$ is replaced with the digit at $9-$i$.$ Save the improved program in ps$01\_01$i$.$py$.$ What is

the encrypted value of $6150?$