Simple heap implementation in Python

heap.py

class Heap:
    def __init__(self, arr):
        self.arr = arr
        self.size = len(arr)
        self.init()
    
    def l(self, i):
        return 2*i+1
    
    def r(self, i):
        return 2*i+2
        
    def p(self, i):
        return (i-1)/2
    
    def init(self):
        for i in range(self.size/2, -1, -1):
            self.heapify(i)
    
    def heapify(self, p):
        if p >= self.size:
            return
        
        left, right = self.l(p), self.r(p)
        if left >= self.size:
            return
        
        if self.arr[p] < self.arr[left] and right >= self.size:
            self.arr[p], self.arr[left] = self.arr[left], self.arr[p]
            return
        
        if right >= self.size:
            return
        
        largest = max(self.arr[p], self.arr[left], self.arr[right])
        if largest != self.arr[p]:
            if largest == self.arr[left]:
                self.arr[p], self.arr[left] = self.arr[left], self.arr[p]
                self.heapify(left)
            else:
                self.arr[p], self.arr[right] = self.arr[right], self.arr[p]
                self.heapify(right)
    
    def insert(self, v):
        if self.size == len(self.arr):
            self.arr.append(v)
            self.size += 1
        else:
            self.arr[self.size] = v
            self.size += 1
        i = self.size-1
        while i > 0 and self.arr[i] > self.arr[self.p(i)]:
            self.arr[i], self.arr[self.p(i)] = self.arr[self.p(i)], self.arr[i]
            i = self.p(i)
    
    def pop(self):
        m = self.arr[0]
        self.arr[0] = self.arr[self.size-1]
        self.size -= 1
        self.heapify(0)
        return m