Pythons are a total non-issue.
Human fatalities from non-venomous snakes are exceedingly rare, on the order of single digits worldwide annually. Most incidents involve captive snakes, that is, people who are killed by snakes that they are purposefully in close contact with. In the US, you are many times more likely to be struck by lightning than killed by a non-venomous snake.
Living in a flooded, dilapidated skyscraper in a setting of post-societal collapse, you have far better things to worry about than snakes. It's not even worth addressing, you're probably more likely to die by trying to board up the windows and getting a cut that becomes infected.