ignoring the logic of your program for a moment, you have to take a couple of syntax problems, in this line:
new_word = [1:len(new_word)] + first + pyg
You can take slices with
, but you have to specify the variable you want the slice of:
example = "hello world"
print example[0:5] # should print hello
see how i use variable name +  to take a slice of a string stored in a variable? See if you can apply this logic to your problem
then the problem is with the slice self:
you can't use variable with you haven't defined yet, you are defining
new_word in this line, you can't use it yet, which variable contains the entire string entered by the user? Maybe you should use that one instead?
If you need more help, post an updated version of your code