Algorithms For Dummies

Choosing between multiple options  

using nested decisions

Nesting is the process of placing a subordinate statement within another state-

ment. You can nest any statement within any other statement, in most cases. To 

see how this works, open a copy of IPython and type the following code:

def SecretNumber():

   One = int(input("Type a number between 1 and 10: "))

   Two = int(input("Type a number between 1 and 10: "))

  

   if (One >= 1) and (One <= 10):

      if (Two >= 1) and (Two <= 10):

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CHAPTER 4

  Introducing Python for Algorithm Programming 

     83

         print('Your secret number is: ' 

+ str(One * Two))

      else:

         print("Incorrect second value!")

   else:

      print("Incorrect first value!")

In this case, 

SecretNumber()

 asks you to provide two inputs. Yes, you can get 

inputs from a user when needed by using the 

input()

 function. The 

int()

 func-

tion converts the inputs to a number.

There are two levels of 

if

 statement this time. The first level checks for the valid-

ity of the number in 

One

. The second level checks for the validity of the number in 

Two

. When both 

One

 and 

Two

 have values between 1 and 10, .

SecretNumber()

 out-

puts a secret number for the user.

To see 

SecretNumber()

 in action, type SecretNumber() and press Enter. Type 20 

and press Enter when asked for the first input value, and type 

10

 and press Enter 

when asked for the second. You see an error message telling you that the first 

value is incorrect. Type SecretNumber() and press Enter again. This time, use 

values of 10 and 20. The function will tell you that the second input is incorrect. 

Try the same sequence again using input values of 10 and 10.