What Stetim is saying is correct. At this line:
new_word = [1:len(new_word)]
You are not saying from what you are slicing.
Tells the console to take characters 2 until the amount of characters in new_word from...
It is not saying where to slice the characters from
first = "word" you are saying take the first letter of the string "word" and not of the value of the variable word. So it will always be "w" in this case. If you remove the quotes you are telling it to take the variable instead of the actual string.
Hope this helps