Python Decision Making and Loops


DECISION MAKING:

If Statement     

 

An if statement consists of a boolean expression followed by one or more statements.
if...else statement

nested if else statement
An if statement can be followed by an optional else statement, which executes when the boolean expression is FALSE.

You can use one if or else if statement inside another if or else if statement(s).

Ex:


var = 100     #indentation is important if ( var ==100):

print "Good bye!"



Else:


An else statement can be combined with an if statement. An else statement contains the block of code that executes if the conditional expression in the if statement resolves to 0 or a FALSE value.
if expression: statement(s)
else:
statement(s)
2) a=10
if(a>10):
              print("Value of a is greater")
  else :
                  print("Value of a is 10")


3)

var1 = 100 if var1:
print "1 - Got a true expression value" print var1
else:
print "1 - Got a false expression value" print var1

var2 = 0 if var2:
print "2 - Got a true expression value" print var2
else:
print "2 - Got a false expression value" print var2

print "Good bye!"



Elif Statement:


The elif statement allows you to check multiple expressions for TRUE and execute a block of code as soon as one of the conditions evaluates to TRUE.

Similar to the else, the elif statement is optional. However, unlike else, for which there can be at most one statement, there can be an arbitrary number of elif statements following an

if expression1: statement(s)
elif expression2: statement(s)
elif expression3: statement(s)
else:
statement(s)
4)
var = 100
if var == 200:
print "1 - Got a true expression value" print var
elif var == 150:
print "2 - Got a true expression value" print var
elif var == 100:
print "3 - Got a true expression value" print var
else:
print "4 - Got a false expression value" print var

print "Good bye!"


5)

var1 = 1+2j

                                 if (type(var1) == int):
                                       print("Type of the variable is Integer") 
                               elif (type(var1) == float): 
                                     print("Type of the variable is Float") 
    elif (type(var1) == complex)
       print("Type of the variable is Complex")
elif (type(var1) == bool):
     print("Type of the variable is Bool") 
  elif (type(var1) == str): 
   print("Type of the variable is String") 
elif (type(var1) == tuple):
   print("Type of the variable is Tuple") elif (type(var1) == dict):
  print("Type of the variable is Dictionaries") 
elif (type(var1) == list):
           print("Type of the variable is List") 17.else:
 print("Type of the variable is Unknown")


6)

x = raw_input("What is the time?")


if x < 10:
print "Good morning" elif x<12:
print "Soon time for lunch"

elif x<18:
print "Good day"

elif x<22:
print "Good evening"

else:
print "Good night"



7)


total = int(raw_input('What is the total amount for your online shopping?')) country = raw_input('Shipping within the US or Canada?')

if country == "US": if total <= 50:
print "Shipping Costs $6.00" elif total <= 100:
print "Shipping Costs $9.00" elif total <= 150:
print "Shipping Costs $12.00"
else:
print "FREE"

if country == "Canada": if total <= 50:
print "Shipping Costs $8.00" elif total <= 100:
print "Shipping Costs $12.00" elif total <= 150:
print "Shipping Costs $15.00" else:
print "FREE"



9)

allowed_users = ['bill', 'steve']


# Get the username from a prompt
username = raw_input("What is your login? :  ")
# Control if the user belongs to allowed_users if username in allowed_users:
print "Access granted"

else:
print "Access denied"
10)
age = 38

1. if (age >= 11):
2.    print ("You are eligible to see the Football match.") 3.       if (age <= 20 or age >= 60):
4.                    print("Ticket price is $12")
5.          else:
6.               print("Tic kit price is $20")
7.     else:
8.               print ("You're not eligible to buy a ticket.")





LOOPS:

In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on. There may be a situation when you need to execute a block of code several number of times.
Programming languages provide various control structures that allow for more complicated execution paths.
A loop statement allows us to execute a statement or group of statements multiple times





Loop Type
Description
while loop
Repeats a statement or group of statements while a given condition is TRUE. It tests the condition before executing the loop body.
for loop
Executes a sequence of statements multiple times and abbreviates the code that manages the loop variable.
nested loops
You can use one or more loop inside any another while, for or do..while loop.

Loop Control Statements
Loop control statements change execution from its normal sequence. When execution leaves a scope, all automatic objects that were created in that scope are destroyed.
Python supports the following control statements. Click the following links to check their detail.
Control Statement
Description
break statement
Terminates the loop statement and transfers execution to the statement immediately following the loop.
continue statement
Causes the loop to skip the remainder of its body and immediately retest its condition prior to reiterating.
pass statement
The pass statement in Python is used when a statement is required syntactically but you do not want any command or code to execute.

For Loop:
iteration statement, which allows a code block to be repeated a certain number of times. .

for <variable> in <sequence>:
      <statements>
else:
      <statements>

Example of a simple for loop in Python:
1)
>>> languages = ["C", "C++", "Perl", "Python"]
>>> for x in languages:
...     print(x)
...
C
C++
Perl
Python
>>> 

2)
edibles = ["ham", "spam","eggs","nuts"]
for food in edibles:
    if food == "spam":
        print("No more spam please!")
        break
    print("Great, delicious " + food)
else:
    print("I am so glad: No spam!")
print("Finally, I finished stuffing myself")

$ python for.py
Great, delicious ham
No more spam please!
Finally, I finished stuffing myself

3)
edibles = ["ham", "spam","eggs","nuts"]
for food in edibles:
    if food == "spam":
        print("No more spam please!")
        continue
    print("Great, delicious " + food)
else:
    print("I am so glad: No spam!")
print("Finally, I finished stuffing myself")

Great, delicious ham
No more spam please!
Great, delicious eggs
Great, delicious nuts
I am so glad: No spam!
Finally, I finished stuffing myself
>> 
The built-in function range() is the right function to iterate over a sequence of numbers. It generates an iterator of arithmetic progressions:
Example:

>>> range(10)
range(0, 10)
>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> 
Syntax;
The built-in function range() is the right function to iterate over a sequence of numbers. It generates an iterator of arithmetic progressions:
Example:

>>> range(10)
range(0, 10)
>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> 

Ex:
>>> list(range(42,-12,-7))
[42, 35, 28, 21, 14, 7, 0, -7]

Ex:
n = 100

sum = 0
for counter in range(1,n+1):
    sum = sum + counter

print("Sum of 1 until %d: %d" % (n,sum))

Whileloop does the exactly same thing what "if statement" does, but instead of running the code block once, they jump back to the point where it began the code and repeats the whole process again.
Syntax
While expression:
        Statement: 

Ex:
x=0   
while (x<4):
             print x
             x= x+1
o/p:
0
1
2
3
 

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