Convert a shifted ASCII value to char inside the abc scope

Background

This question is inspired by The Caesar Cipher. Given a modified ASCII value i where i > 122 or i < 97, the goal is to find the char represented by its value. For example, since 'z' value is 122, then 123 references 'a', as well as 149 and 97 +- 26n.

Goal

The function calc_chr should calculate shifted ASCII values while staying inside the scope of the abc, i.e. [97, 122] decimal.

Clear Example

let 'x' be 120
let new_val be 'x' + 5 -->125
calc_chr(new_val) is equal to 'c'

The function returns 'c', as a result of shifting 'x' 5 times: x -> y, z, a, b, c.

Workaround

The workaround isn't efficient.

while new_val > 122:
    new_val -= 26
while new_val < 97:
    new_val += 26

The desired solution, if exists, is a calculation (not a loop).

2021 Update

This question was written terribly in 2019. Since then, I have learned a thing or two... Therefore, I would appreciate if the community, i.e. you, could rejudge this post and consider giving it a 0 score, or even a positive score if deserved :)

I will accept an answer in 24 hours. The current accepted solution was suggested by Ture. Thanks in advance.

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