I am practicing slicing, and I want to run a program that prints a name backwards.
Mainly, I want to know how to access the last item in the sequence.
I wrote the following:
name = raw_input("Enter Your Name: ")
backname = ???
print backname
Is this a sound approach? Obviously, the ??? is not a part of my syntax, just asking what should go there.
To access the last item in a sequence, use:
print name[-1]
This is the same as:
print name[len(name) - 1]
Reversing a sequence has a common idiom in Python:
backname = name[::-1]
The Good primer for Python slice notation question has more complete information.
backname[-1] #the last item in the sequence
#To reverse backname (the long way):
aList = [c for c in backname] #will give you ['1', '2', ..., 'n']
aList.reverse() #aList will be ['n', ..., '2', '1]
backname = "".join(aList) #backname reversed
#To reverse backname, as other answers replied:
backname[::-1]
You want name[::-1]. The -1 is the "step" of the slice-- if you wanted every other letter, for example, you would use name[::2].
You can use negative indices to access items counting from the end of a list, so name[-1] will give you the last character. However, the third slice argument is a step, which can also be negative, so this will give you the whole string in reverse:
name[::-1]
With slice syntax, you would use:
backname = name[::-1]
The two colons show that the first two parameters to the slice are left at their defaults, so start at the beginning, process to the end, but step backwards (the -1).
You probably want to read the docs: http://docs.python.org/library/stdtypes.html#sequence-types-str-unicode-list-tuple-buffer-xrange
There's a method to reverse the string for you, if you want. For the specific question you asked, to access the last item of a sequence you use "seq[-1]".
