Search in a Sorted Infinite Array (medium)

import math
import sys 

class Solution:
  def searchInfiniteSortedArray(self, reader, key):
    
    # figure out the reader size by doing binary search between 0 and the 
    # largest integer possible = sys.maxsize
    def find_array_last_index():
      b, e = 0, sys.maxsize
      index = 0
      while b <= e:
        m = (b + e) // 2
        if reader.get(m) == math.inf:
          e = m - 1
        else:
          b = m + 1
          index = m 
      return index
    
    # do a binary search to find the first occurrence of the key 
    def search(length):
      b, e = 0, length
      index = -1
      while b <= e:
        m = (b + e) // 2
        if reader.get(m) >= key:
          index = m
          e = m - 1
        else:
          b = m + 1
      return index if reade