cashaddress is python library which is able to convert legacy BCH address to new format.

The requirements of this library are:

pip install base58

To install this library and its dependencies use:

pip install cashaddress

The first thing you need to do is import the library via:

from cashaddress import convert

It does not matter if you use legacy or new address as input.

Then you can convert your address via:

address = convert.to_cash_address('155fzsEBHy9Ri2bMQ8uuuR3tv1YzcDywd4')

or

address = convert.to_legacy_address('bitcoincash:qqkv9wr69ry2p9l53lxp635va4h86wv435995w8p2h')

You can also validate address via:

convert.is_valid('155fzsEBHy9Ri2bMQ8uuuR3tv1YzcDywd4')

or

convert.is_valid('bitcoincash:qqkv9wr69ry2p9l53lxp635va4h86wv435995w8p2h')