While loops - II

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Hello Folks...!!!

Today we shall see how to use while loops for iterating through the data structures....

Example 1: 

Consider the sentence: s="learning python is very easy." . Now the task is to capitalize each word of the sentence. See the code below:

• We first split the sentence into list of words.  
• Then we store the length of the list in the variable 'n'. We initialize the loop control variable 'i' to '0'
• We define a loop stating that, until 'i' remains less than the length of the list.
• Inside the loop, we use capitalize() to capitalize each word and store it back in the same index in the list.
• We join the list and store it back in the string variable 's'.

Example 2:

Minu is trying to decode a secret message.The message is  "yawa rotcod eth speek yad a elppa na". She found that every word is reversed and the whole sentence is also reversed. Now let us help her decode it programatically.

Example 3:  

Now I will code a simple placement problem - 'Array rotations'

If you come across such a problem, it is nothing but rotate the list for specified number of times. 

For example:

Given list : [1,2,3,4,5]

No.of.rotations: 2

Resultant list: [3,4,5,1,2]

Let us look at the solution now :

First we store the element at index '0' in a temporary variable, then we remove it out and the add it at the end of the list.

break and continue in loops:

One can either break the loop or continue without executing the statements below using the keywords 'break' and 'continue'.

Example 4: Consider the pattern below :

                            1

                          333

                        55555

                      7777777

                    999999999

A pyramid of odd numbers below 10. Let us look at the coding :

What we do here !?

• The first loop checks whether the number is less than 10.
• The if condition checks whether it is an odd number or an even one.
• If it is an even number, then without executing the next if-condition and statements below, it continues the first while loop. If you do not use a continue here, it will check the next if-condition also.
• If it is an odd number then the further proceeding for printing it out is carried out.
• We have a variable 'space' initialized to 10. It is used to print the number in appropriate place leaving space before it. 
• Thus the second while loop is concerned with the alignment.
• The third while loop prints the number.
• When 'i' increases, space has to decrease. So we decrement space in the outer most loop.

This is how we print a pyramid pattern.

Example 5:

Let it be a game. You must get input from the user and display it. Once the user hits a number greater than 10, It must exit the loop and stop getting input from user.

With this simple last example, we will finish the while loops concept.

Python provides you a provision to use 'else' with 'while' loops. You can give the instructions to be executed if the while loop fails in the else part. For example:

Example 6:

Here when the count is less than 5, its square is printed. When it is exceeded, the loop is not simply terminated, but a message is also displayed.

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