Comparing string objects within a list - Python

Question

message = ["TS", "EE", "RE", "Z"]

So I'm trying to compare the characters within this list, and have conditions when some things arise such as if a value in the list for example "EE" is the same, it will return true and append a "Q" to separate the letters so the list looks like this

 message = ["TS", "EQ", "ER" "EZ"]

So I tried it normally without looping it works but when I loop it says string index out of range.

a = ''
a = message[1]
if a[0] == a[1]:
    print("True")
else:
    print("False")

When looping

for i in range(len(message)):
    a = ''
    a = message[i]
    if a[0] == a[1]:
        print("True")

What should I do? Turn it into a string first and work on it?

Your problem is the last element is length 1 so you tried to access the the second element when there is no second element i.e. Out of index error — Chinny84
– Chinny84, Commented Oct 1, 2017 at 4:22
Those a = '' lines are not accomplishing anything, since you replace the value of a on the next line. — jasonharper
– jasonharper, Commented Oct 1, 2017 at 4:27
For the last item in the array (the letter Z) there is no position 1 since the string only consists of 1 character. — andy9775
– andy9775, Commented Oct 1, 2017 at 4:28

沈靖程 · Accepted Answer · 2017-10-01 11:39:09Z

1

Note that there is an element "Z" in the array (i.e. message[-1]) that has only one char in it.

def getIndex(message):
  for i in range(len(message)):
    a = message[i]
    if a[0] == a[1]:
      return i
index = getIndex(message)
tmp = message[index][1]
message[index][1] = 'Q'
for x in range(index+1, len(message)):
  tmp1 = message[x][0] 
  if len(message[x])==1:
    message[x][0] = tmp
    message[x][1] = tmp1
    return
  else:
    message[x][0] = tmp
    tmp = message[x][1]
    message[x][1] = tmp1

edited Oct 1, 2017 at 11:39

answered Oct 1, 2017 at 4:26

沈靖程

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