[Tutorial] String Reversal Techniques (inspirezonetech#142)

* I added two ways of reversing strings , but I was contemplating on adding the deque method but thought it was too complex

* fixed the flake8 errors

string-formatting/string-reversal.py

@@ -1,9 +1,37 @@
 # ------------------------------------------------------------------------------------
-# Tutorial: brief description of tutorial content
+# We're going to look at a few different ways that you can reverse the structure of a string .
+# Let's begin.
 # ------------------------------------------------------------------------------------
 
-# Code here explaining concept with comments to guide
+# Single Words , A string is an iterable and anything within these --> ""
+# 1. The built-in reverse method
+# This method is used on iterables , commonly on lists and strings
+# Example of functions that reverse a string.
+def reverseString(word):
+    reversedWord = "".join(reversed(word))
+    return reversedWord
+'''
+Let's break down what's above:
+Remember that all strings are immutable but iterable. So if that's the case , we can't use the .reverse() function like we could on a list.
+So we iterate through each letter and use the reversed() function . Now since the reversed() function return an iterable;a list .
+We use the join() to concatenate the letters and then we return the reversed String.
+'''
+# 2.The reverse slice method
+# This method also works on iterables too.
+# Let's use the same example with this method too
+def backString(word):
+    reversedWord = word[::-1]
+    return reversedWord
+'''
+Let's break this down as well:
+The slicing technique is used to get a certain portion of string and using the starting and ending index values.
+e.g [a:b], this slices from position to position before b ; so b-1 . What we don't commonly use is the third option of [a:b:c] <-- C.
+What c does is specify the number of characters to jump or skip over . So if c == 2 , we're gonna skip over 2 characters .But if c == -1,this specifies that the string begins from the back.
+We commonly use -1 when we want the last letter or character in a string e.g word = "pet",word[-1] == t.
+Back to the function , if we don't specify the starting and end values , the computer just assumes it's the whole string .
+So e.g [a:] this is from a to the last , [:b] from the first to b , [a::c] from a to the last every c characters , [:b:c] from the first to b every c characters .
+So [::-1]  means from the first to last in reverse .
+'''
 
 # ------------------------------------------------------------------------------------
-# Challenge: list challenges to be completed here. minimum of one challenge per tutorial
-# ------------------------------------------------------------------------------------
+# The format is the same even for sentences : So write a function that reverses the sentence "I love ketchup".