Controlflow.md

Expression

• Comparison Operators

  // Given that x = 5

  Operator	Description	Comparing	Returns
  ==	Equal to	x == 8	False
  		x == 5	True
  !=	not equal	x != 8	True
  		x != 5	false
  >	greater than	x > 8	False
  <	less than	x < 8	True
  >=	greater than or equal to	x >= 8	False
  <=	less than or equal to	x <= 8	False

• Logical Operators

  Given that x = 6 and y = 3, the table below explains the logical operators:

  Operator	Description	Example
  and	and	(x < 10 and y > 1) is True
  or	or	(x == 5 or y == 5) is False
  not	not	not(x == y) is true

quiz

1. i = 10, j = 3, k = 20, what is the value of the following logical expression:

   j < 4 or j == 5 and i <= k

2. The expression P and Q is TRUE if either P or Q is TRUE or both are TRUE.

3. If p is a Boolean variable, which of the following logical expressions always has the value false?

   A. p and p

   B. p or p

   C. p and !p

   D. p or !p

   E. b and d above

4. True or False? The expression not (n < 5) is equivalent to the expression n > 5.

   A. True

   B. False

Control Flow

1. If Statement

   book = "maths"
   
   if book == "history":
       print("History Book")
   elif book == "maths":
       print("Math Book")
   else:
       print("Unknown Book")  
   

   Quiz

   Implement abs function

     def abs(x):
         #Implement your code below 
   
     print(abs(10)) # should print 10
     print(abs(-10)) # should print 10
   

   If time is less than 10:00, create a "Good morning" greeting, if not, but time is less than 20:00, create a "Good day" greeting, otherwise a "Good evening":

       def greeting(hour):
         # Implement your code here
   
      print(greeting(8))   # print "Good morning" 
      print(greeting(13))  # print "Good day"
      print(greeting(22))  # print "Good evening"             
   

2. while statement

   count = 0
   print("Starting loop")
   
   while count<10:
       print("Current count : " + str(count))
       count +=1  # equivalent to "count = count+1"
   
   print("End loop")
   

   Quiz

   What does the following code output?

   i = 0
   while i < 3:
       print("hi")
       i += 1
   

   Print repeat star

   def loop(count):
     ## Implement your code
     
   loop(5)  // should output 
   /* should output 
       *
       **
       ***
       ****
       *****
   */
   
   # Hint, check this link. https://www.w3schools.in/python-tutorial/repeat-string-in-python/
   

3. for loop

   for i in range(8):
     print(i)
   
   for i in range(2,6):
     print(i)
   

   Quiz

   sigma function

     def sigma(begin, end):
       // implement your code
     
     print(sigma(2, 5)) // should output 2+3+4+5=14            
   

4. Break

   for letter in 'Python':     # First Example
      if letter == 'h':
         break
      print 'Current Letter :', letter
   

5. Continue

   for letter in 'Python':     # First Example
      if letter == 'h':
         continue
      print 'Current Letter :', letter