title: What does ::-1 mean for python string index?
body: <p>I was looking at python code that printed palindromes, and I stumbled upon this line of code:</p>
  
  <p><code>for i in range(1000, 7, -1):
      if (str(i) == str(i)[::-1])
  </code></p>
  
  <p>I'm trying to learn Python right now, and I'm just not that familiar with the syntax. Currently, I understand that this line of code checks to see if the first digit of integer i matches its last digit. Does the syntax of this line mean that the index is being incremented in order to check if it's a palindrome? What is the purpose of having two colons?</p>