In your filter expression, you are given variables problem and contest, and it's supposed to returns 1 if the problem matches your search, 0 otherwise.

Example: problem.rating == 2400 and "geometry" not in problem.tags and contest.divison == "Div. 1"

The variable problem contains such properties:

id - The ID of the problem, in the format e.g. 1234H, 2024A.
rating - The CF rating tag. Can be absent.
contest - The contest id of this problem. Equals to contest.id.
index - The problem index in its contest, such as A or C.
pts - The problem points worth in its contest, 1500 for example.
tags - Problem tags. Used to filter out 'data structure' or 'geometry'.

The variable contest contains such properties:

id - The ID of the contest. It is different from the round number.
type - The scroing rules of such contest. Enumeration of "CF", "IOI" and "ICPC".
name - The contest name. Example, "Codeforces Round #7744 (Div. 10)".
division - The contest division in string. Enumeration of "Div. 1+Div. 2", "Div. 1", "Div. 2", "Div. 3", "Div. 4", "Educational" and "Unknown". (Wanna know how it works? Just do string matching in the contest name dummy)

Most of these properties are directly copied from the API.

Note you need module pyjson installed for it to work.

import urllib.request as request
import json,random

class Problem:
    def __init__(self, apiobj):
        self.id = f"{apiobj['contestId']}{apiobj['index']}"
        self.rating = apiobj['rating']
        self.tags = apiobj['tags']
        self.contest = apiobj['contestId']
        self.index = apiobj['index']
        self.pts = apiobj['points']

class Contest:
    DIV_NAMES = ["Div. 1+Div. 2", "Div. 2", "Div. 1", "Educational", "Div. 3", "Div. 4"]
    def __init__(self, apiobj):
        self.id = apiobj['id']
        self.type = apiobj['type']
        self.name = apiobj['name']
        self.division = "Unknown"
        for div in Contest.DIV_NAMES:
            if div in apiobj['name']:
                self.division = div
                break

contests = {}
problems = []

def strawberry(problem,contest): # A test filter function
    return problem.rating == 2400 and contest.id >= 1000 and contest.division == "Div. 1" and "geometry" not in problem.tags

def fetchall():
    global contests, problems
    contests = {}
    problems = []

    try:
        contests_raw = request.urlopen("http://codeforces.me/api/contest.list?gym=false").read().decode()
        problems_raw = request.urlopen("http://codeforces.me/api/problemset.problems").read().decode()
    except:
        print("Codeforces API playing Genshin Impact at the moment")
        return False
    
    contests_obj = json.loads(contests_raw)
    problems_obj = json.loads(problems_raw)

    if contests_obj["status"] != "OK" or problems_obj["status"] != "OK":
        print("Codeforces API thinks your skill is too mediocre to use it")
        return False

    for problem_obj in problems_obj["result"]["problems"]:
        try:
            problem = Problem(problem_obj)
            problems.append(problem)
        except:
            pass

    for contest_obj in contests_obj["result"]:
        try:
            contest = Contest(contest_obj)
            contests[contest.id] = contest
        except:
            pass

    return True

print("Fetching problems...")
if not fetchall():
    exit(0)
candidates = []
schema = input("Enter filter expression ")
for problem in problems:
    try:
        if eval(schema,None,{'problem':problem,'contest':contests[problem.contest]}):
            candidates.append(problem)
    except Exception as e:
        print ("Error evaluating filter expression:",e)
if not len(candidates):
    print ("No problems matches your filter.")
else:
    result = random.choice(candidates)
    print(f"Your problem is: {result.id}")

...