title: How to check index values in a loop without incrementing the index?
body: <p>The challenge is from codingbat - Sum the elements of the array except for all values between 6 and 7, not counting the 6 or the 7 either.</p>
  <p>My strategy was create a new array &quot;valid&quot; and append valid elements of the array nums to the &quot;valid&quot; array, and then sum the valid array.</p>
  <p>Because I need the index to check for a 7 once a 6 is detected, my plan was to enumerate the array, and when the value 6 is found, to loop through the remainder of the array until a 7 is found, not appending the values 6-7 to the array &quot;valid&quot; in the process.</p>
  <p>I ran my code through the MIT Python tutor to see where it was going wrong, and when I increment the index after i+1 != 7 (with the intention of checking to see if the next value in the array is a 7) it increments the index (it finishes working with that index of the array and moves on to the next one, rather than sticking in the code for the 6 and continuing to loop through and check for a 7).</p>
  <p>Appreciate any help with this, especially a solution that sticks to the original strategy but implements it correctly in the code.</p>
  <pre><code>def sum67(nums):
    valid = []
    for i,c in enumerate(nums):
      if c == 6:
      #when a 6 comes up
        if  nums[i+1] == 7:
        #if the next number is a 7
          i+=1
          break
          #increment and break
        else:
          i+=1
          #increment
      else:
        valid.append(c)
    return sum(valid)
          
  sum67([1, 2, 2, 6, 99, 99, 7])
  </code></pre>
  <p>Edit 1:
  The desired output for</p>
  <pre><code>sum67([1, 2, 2, 6, 99, 99, 7])
  </code></pre>
  <p>is 5. (Because 1 + 2 + 2 = 5, and the 6, 99, 99, and 7 are excluded because they are or are between a 6 and a 7)</p>