Own Solution

class RecentCounter:

    def __init__(self):
        self.counts = []
        self.number = None 

    def ping(self, t: int) -> int:
        self.number = 0 
        self.counts.append(t)
        start_range = t - 3000
        index = 0
        while index < len(self.counts):
            if self.counts[index] >= start_range:
                return len(self.counts)
            else:
                self.counts.pop(0)
                index = 0
            
# Your RecentCounter object will be instantiated and called as such:
# obj = RecentCounter()
# param_1 = obj.ping(t)