How to split a text entry in a pandas dataframe into multiple entries (lines) by delimiter?

Question

Python

Good afternoon.
I have a notepad with the following:

import pandas as pd
df = pd.read_csv("yyy.csv")
df.shape
>>(52350, 14)

One of the "PP" columns with strings (comma-separated integers), let the rest be the "C" column to illustrate the behavior.
In the table, the data looks like this:
PP | C
---------+-------
1, 2 | T
5 | C
18, 20 | S
7 | T
We must do this:
PP | C
---------+-------
1 | T
2 | T
5 | C
18 | S
20 | S
7 | T
Elements in the PP column can be left as text, they will then be grouped by them. The number of elements is from 1 (85% of records) to 3 (2-3% of records). When an element is moved to a new record, the information on the remaining columns is simply duplicated.
Is it possible to somehow contrive to do this without "manual" iteration in a loop through all the records, given the number of records?
There are a lot of examples on the Internet on splitting into columns. Unfortunately, I did not find the "by lines" option.
Thank you.