Home/ Questions/typeerror: slice indices must be integers or none or have an __index__ method - Simple solution when encountering the error
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Liam Grange
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Asked: 2022-05-11T19:07:38+00:00 In:

typeerror: slice indices must be integers or none or have an __index__ method – Simple solution when encountering the error

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As title, I am getting typeerror: slice indices must be integers or none or have an __index__ method error. How can I fix it so the error goes away? Here is my program:

from collections import deque
 
 m = []
 f = open("IntegerArray.txt")
 for line in f:
  m.append(int(line))
 
 class InversionCount:
 
  def __init__(self, n):
  self.n = n
  def inversionMergeSort(self, m):
  if len(m) <= 1:
  return m
  half = len(m)/2
  left = m[0:half]
  right = m[half:]
  left = self.inversionMergeSort(left)
  right = self.inversionMergeSort(right)
  return self.inversionSort(left, right)
 
  def inversionSort(self, left, right):
  leftQueue = deque(i for i in left)
  rightQueue = deque(j for j in right)
  orderedList = []
  while len(leftQueue) > 0 or len(rightQueue) > 0:
  if len(leftQueue) > 0 and len(rightQueue) > 0:
  if leftQueue[0] <= rightQueue[0]:
  orderedList.append(leftQueue[0])
  leftQueue.popleft()
  else:
  orderedList.append(rightQueue[0])
  self.n += len(leftQueue)
  rightQueue.popleft()
  elif len(leftQueue) > 0:
  orderedList.append(leftQueue[0])
  leftQueue.popleft()
  elif len(rightQueue) > 0:
  orderedList.append(rightQueue[0])
  rightQueue.popleft()
  return orderedList
 
 nInversions = InversionCount(0)
 nInversions.inversionMergeSort(m)
 print (nInversions.n)

When I operate it and I received the error text:

Traceback (most recent call last): File "C:/Python34/inversion3.py",
 line 44, in <module>
  nInversions.inversionMergeSort(m) File "C:/Python34/inversion3.py", line 16, in inversionMergeSort
  left = m[0:half] TypeError: slice indices must be integers or None or have an __index__ method

I appreciate any help from you.

typeerror
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2 Answers

  1. Best Answer
    Expert

    The cause:  The error is detected because your slice index is malformed, it must be in one of the following categories: integers/ none/ have an __index__ method

    Solution: 

    You should change to an int as this way:

    left = m[0:int(half)]
    • 9

  2. In 3.x, int/int provides a floating. This is not an int. 

    >>> 3/2
1.5

    so your line 15 

     half = len(m)/2

    Makes half a floating. You will need a double slash 

     half = len(m)//2

    To make half of an int, as necessary for its use in line 16

    • 7

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