[what] Basic Program Control Structures In Python

 

The basic program control structure concept consists of 4 elements:

1. Sequence - by default, program instructions are executed from to bottom.
2. Selection - whenever a decision is required, selection control is implemented i.e. program will branch into two or more paths and the program decides the path selection based on certain math/logic statement evaluation.
3. Loop - whenever there is a need to repeat certain instructions, loop control is implemented.
4. Module - related instructions are grouped into modules for better code management and code readability.

SEQUENTIAL

# SEQUENTIAL 
# 01.hello world

print("hello world")

print("\n====================\n")

# SEQUENTIAL 
# 02.print 1+2

print(1+2)

print("\n====================\n")

# SEQUENTIAL
# 03.input, print add var

var1=int(input("var1:"))

var2=int(input("var2:"))

print("\n====================\n")

print("%d + %d = %d" % (var1,var2,var1+var2))

print("\n====================\n")

# SEQUENTIAL
# 04.input, print mul var

print("%d * %d = %d" % (var1,var2,var1*var2))

print("\n====================\n")

SELECTION

# IF-SELECTION
# 05.input, print div var

if (var2==0):
  print("Error. Division by 0.")
else:
  print("%d / %d = %f" % (var1,var2,(var1/float(var2))))

print("\n====================\n")  

LOOP

# FOR-LOOP
# 06. loop from 0 to 2
print ("[06] Start counting.")
for x in range(3):
  print(x)
else:
  print("Done.")

print("\n====================\n")

# LOOP
# 07. loop from 0 to 4, display loop counter
listArr = [1,2,3,4,5]
print ("[07] Displaying listArr values.")
for x in range(len(listArr)):
  print(listArr[x])
else:
  print("Done.")

print("\n====================\n")

# LOOP
# 08. input index and value, update list
listArr = [1,2,3,4,5]
print ("[08A] Displaying listArr values.")
for x in range(len(listArr)):
  print(listArr[x])
else:
  print("Done.")

indexNumber = int(input ("Enter index number:"))
newValue = int(input ("Enter new value:"))

listArr[indexNumber] = newValue

print ("[08B] Displaying listArr values.")
for x in range(len(listArr)):
  print(listArr[x])
else:
  print("Done.")

print("\n====================\n")

# MODULE
# 09. Modular program
# displayData, updateData, and displayData again
# subModule_displayData
def displayData(listArr):
  for x in range(len(listArr)):
    print(listArr[x])
  else:
    print("Done.")
  print("\n====================\n")  

# subModule_updateData
def updateData(listArr):
  indexNumber = int(input ("Enter index number:"))
  newValue = int(input ("Enter new value:"))  
  listArr[indexNumber]=newValue
  print("\n====================\n")

# mainModule
listScore = [10,20,30,40,50]
print ("[09A] Displaying score values.")  
displayData(listScore)  
print ("[09B] Input new scores.")  
updateData(listScore)
print ("[09C] Displaying updated score values.")
displayData(listScore)