Submission AC code for Concert Tickets in PyPy3, use sys.stdin.readline() for input, this is a lot more faster than normal input.

Also it is gonna be really frustating to do the problem set in Python due to the time constraints of CSES, I end up optimizing small stuff like using bitwise operations rather than arithmetic and stuff like that.

You can also solve it using a DSU to simulate the removal of an ticket after selling it to a customer(point parent to the previous ticket in the sorted order). here's my solution in python:

import bisect
import sys
 
sys.setrecursionlimit(3 * 10**5)
n, m = map(int, input().split())
prices = sorted(list(map(int, input().split())))
parent = list(range(n + 1))
 
 
def getpar(u):
    if u < 0 or u == parent[u]:
        return u
    parent[u] = getpar(parent[u])
    return parent[u]
 
 
for customer in map(int, input().split()):
    idx = bisect.bisect(prices, customer) - 1
    available = getpar(idx)
    if available >= 0:
        print(prices[available])
        parent[available] -= 1
    else:
        print(-1)

Anyway, you're better off using C++ as it has set/multiset data structure and most of the problemset has tight limits like this problem.

Thank you so much for your answers guys ! The thing is, I really want to improve in Python rather than C++ since it's the go-to language for machine learning and AI, which I want to focus on. So this brings me to another question : - Do competitions like Codeforces or in-person events like ICPC have the same time limit issues with Python as CSES does?