If, elif , else briefly explaination

1. UNIT 4:SCRATCH OR PYTHON (THEORY AND PRACTICAL) 3. COMPOUND STATEMENT
A compound statement represents a
group of statements executed as a unit. The compound statements
of python are written in a specific pattern as shown in example.
Conditions and >>> testl=2
>>>test2=4
testi:
Loops in Python >>>
t test2:
print (test1)
Let's Recal
Write advantages and disadvantages ofPython.
What doyou mean by interactive mode programming and scripting mode of
programming?
STATEMENTS FLOW OF CONTROL
Statementl
SEQUENCE
Sequence means the statements are being executed sequentially. This represents the
default flow of statement.
Statement2
Let's Learn At the end of this chapter, you should be able to:
Comprehend and
useconditionalstatements: if, if-else statements
dComprehend and use loop structure: for, while
Statement3
Fig. 1 Flow of Control
Condition
SELECTION
The selection constructs means the execution of statements depending upon
a condition. If condition evaluates to true. a course -of-action (a set of
statements) is followed otherwise another course-of-action (a different set of
statements) is followed.
true false
Let's Begin Statement(s)
Python provides control statements that serves to state what has to be done by the program, when and
under which condition(s). This chapter discusses conditional and looping statements in detail.
Fig. 2 Flow of
STATEMENTS false
Selection Construct
Decision
tarementsarethe instructions given to
the computer to perform any kind of action such as, data ITERATION
movement, decision making, repetitive action etc. Statements form the smallest executable unit within a The iteration construct means repetition of a set-of-statements depending
upon a condition till the time a condition is true (or false depending upon the
loop). a set-of-statements are repeated again and again until the condition
becomes false (or true).
true
Python program. Statements are
always terminated by semicolon.
Sequence
TYPES OF STATEMENTS IN PYTHON
1. EMPTY STATEMENTS
The simplest statement is the empty statement, which has nothing. In python empty statement is
po
IF STATEMENT Fig. 3 Flow of Iteration
statement. The if statement is the conditional statement in python and it follows selection constructs (decision
constructs).
2. SiMPLE STATEMENT
The simplest form of if statements tests a condition and if the condition evaluates to true, it carries out
some instructions and does nothing in case condition evaluates to false.
It is comprised within a
single logical line.
For example: Syntax:
name=input ("ert.I u! ame") # thls is a
staement
if test expression:
-
statement(s)
Here, the program evaluates the test expression and will execute statement() only if the text
expression is True.
Conditions and Loops in Python

2. Output:
If the text expression is False. the statement(5) is not executed.
Test
false
In Python, the body of the if statement is indicated by the indentation. Body
tarts with an indentation and the first unintended line marks the end.
Expression Python console
Console 1/A 3
true
Python interprets non-zero values as True. None and 0 are interpreted as False.
Example 1: Print a given statement if the number is positive.
Body of if [8]:
In
Python 3.7.0 Shell
In [8]: runfile("D:/python class /statementsi.py', wdir='D: /python class ')
x is less than y
File Edit Shell Debug Options Window Help
PYEhon 3.7.0 (v3.7.0:lbf9cc5093, Jun 27 2018, 04:06:47) [MSC v.1914 32 bit (Inte
1)) on win32 Fig. 4 Flowchart for
if Statement
2pcopyright
", "credits" or "license ()
"
for more information.
nun=3
>>> num>0:
In [9]:
print (num, "is a positive number. ")
rint("*his is àways Tntea. ")
Example 3: Program to test the divisibility of a number with another number.
3 is a positive number
this is always printed. Spyder (Python 3.6)
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F-ELSE STATEMENT
Editor D:python_ dass 11felse stat.py
n else statement can be combined with an if statement. An else statement contains the block of code
nat executes if the conditional expression in the if statement resolves to 0 or a FALSE value.
The else statement is an optional statement and there could be at
nost only one else statement following if.
Syntax:
temp.Py ifelse stat.py
1
number1=int(input("enter first number: "))
2
number2=int(input(""enter second number: "))
3 remainder=number1%numberr2
4 if remainder==0:
Test False
Expression
The syntax of the if..else statement is -
print(number1, "is divisible by",number2)
if expression:
6 else:
True
statement(s)
print(number1, "is not divisible by", number2)
else:
Body of if Body ofelse
statement()
10
Example 2: Find out which is
greater Fig. 2 Flowchart for if..
Output:
Spyder (Python 3.6)
else statement
File Edit Search Source Run Debug Consoles Projects Tools View Help
IPython console
Console 1/A 3
Python 3.6.5 JAnaconda, Inc.| (default, Mar 29 2018, 13:32:41) [MSC v.1900 64 bit
(AMD64)]
Type copyright", "credits" or "license" for more information.
Editor D:python dass
_11statements1.py
{ temp.py" statements.py statementsi.py
-
1 Codin7: utf
2***
3 Created on iue Sep 18 i4:22:39 2018
IPython 6.4.0 -- An enhanced Interactive Python.
5"
In [1]: runfile( 'D:/python class /if else stat. .py', wdir='D: /python clàs ')
7 K=4
8y=5
9if(x*y):
10
print("x is less than y")
! else:
enter first number :123
enter second number: 23
print("y is greater than x"
123 is not divisible by 23
13
Conditions and Loops in Python
Computer Applica
cations

3. In a nested if construct. you can have an if..elif...else construct inside another if...elif...else construct.
IF-ELIF STATEMENT
ometimes a situation arises when there are several conditions. To handle such a situation. Python all
adding any number of. elif clause after an if and before an else clause.
allows Syntax:
if expressionl:
statement(s)
elif expression3: elif expression4:
statement{s)
Syntax: statement(s)
else:
ifexpressionl: elif expression2 : elifexpression3: if expression2: else: else:
statement1 statement_3 statement_5 statement_7 statements) statement() statement(s)
statement_2 statement_4 statement_6 statement_8 Example 5: Print a value depending on the given condition.
***********°°*
Spyder Python 3.6)
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.
Example 4: Program to input the marks of 5 subjects and display the grade.
Spyder (Python 3.6)
Editor-D:Python dass lnested f.py
Fie Edit Search Source Run Debug Consoles Projects Tools View Help
temp-Py eise zat.-py untted1.py 3 grade.py nestedif.py
1 var 16
2 if (var 200)
print ("Express ion value is less than 200")
if (var =
150)
print ("Which is 150")
elif (var = 100):
print (hich is 180")
elif (var ==
S0):
print( "uhich is 50")
elif( var < 50):
Editor - D:python dasS 11gradePY
tep-Py f elsesat.PY untrtledi.py grade.py
?subi=int(input("Enter marks of the first subject: "))
sub2-int (input("Enter marks of ihe second subject: "))
4 sub3=int(input("Enter marks of the third subject: "))
5
sub4=int(input("Enter marks of the fourth subject: "))
subS=int(input("Enter marks of the fifth subject: "))
avg=(subl+sub2+sub3+sub4+sub5) /5
S if(avg>90):
print("grade A")
telif(avg>=88 and avg<98)
11 print "Expressi0n value is less than 50")
2 else:
print (" Could not find true expression ")|
14
prirt grade )
12 elif(avg>=76 and avg<80):
13
print grade ")
14
elif(avg>=60 and avg<70)):
Output:
15 print("grade D")
16 else:
Python console
print("grade )
Console 1/A
Output: Expression value is less than 200
Which is 180
Enter manrks of the first subject: 78
In (3]:
Enter marks of the second subject: 98
Enter marks of the third subject: 95
LOOPING CONSTRUCTS
Enter marks of the fourth subject: 89 Loopsare used to repeatedly execute the same code in a program. Python provides two types of looping
Enter marks of the fifth subject: 85
constructs:
Erade While statement (condition based loop)
For statement (loop for a given number of times)
NESTED IF STATEMENT
InformationByte
There may be a situation when you want to check for another condition after a condition resoivE
true. In such a situation. you can use the nested if construct.
The iteration statements allow a setof instructions to be performed repeatedly until a certain condition is full filled. The
iteration statements are also called loops or looping statements.
252
Computer Application5
Onditions and LoopsinPy
253

4. RANGE) FUNCTION
What follows next is block of statement().
The statement(s) in BLOCK 1 keeps on
executing till condition in while remains True: once the
Before we start with loops, let us discuss range() function which Is used in for loop. range() fun..
generates a list and has a special sequence type. A sequence in python is a succession of values bound condition becomes False and if the else clause is written in while. then else will get executed. While loop
together by a single name. may not execute even once, if the condition evaluates to false, initially. as the condition is tested before
entering the loop.
Example 6: Print numbers 1 to 10.
Some python sequence types are: strings, list. tuples etc.
The common use of range() function are:
Spyder Python 3.6)
range(<lower limit>, <upper limit>) #both limits should be integers
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The function in the form range (1.u) will provide a list having values starting from l,1+1,1+2.
(u-1).
range(0,8) Editor D:python dass_11while.Py
list as[o.1.2.3,4.5.6.7] temp.py ifelse stat..py untitled1.py grade.py 3 nested f.py while.py
1 i-1
range(<lower limit>,<upper limit>,<step value>) #al values should be integers
range(l.u.5)
2 while(i <=10):
print (i),
i it1
gers
it will produce list having values as l, I+s, I+25..=u-1
range(0,10,2)
it will produce list as [O,2.4.6.8] Output:
range(5.0.-1) In [3]: runfile( 'D:/python_ class /vhile.py', wdir='D:/python_ <lass ")
list[5.4.3,2.1] 2
3
range(<number>)
it creates a list from O(zero) to <number>.
For example:
Range(5) 9
List as[o.1.2.3.4] 10
WHILE LoOP You can almost read the statement like English sentence. The first statement initialized the variable
(controlling loop) and then while evaluates the condition. which is True so the block of statements
It is a condition based loop.
written next will be executed.
Syntax:
Last statement in the block ensures that, with every execution of loop. loop control variable moves
while condition: # caondition is Boolean expression returning either True or False near to the termination point. If this does not happen then the loop will keep on executing infinitely.
STATEMENT BLOCK 1
As soon as i becomes 11, condition in while will evaluate to False and this will terminate the locop.
Telse: # optional part of while
STATEMENT BLOCK 2] NESTED WHILE LOOP
We can see that while looks like if statement. The staternent explains with keyword while foll
by a Boolean condition followed by colon (:).
Block of statement belonging to while can have another while statement, i.e., a while can contain another
ed
while.
254
Conditions and Loops in Python
255
r A P p l i c a t i o n

5. Example 8: Program to find the sum of all numbers stored in a list.
Example 7: Program with nested loop. Spyder (Python 3.6)
Spyder (Python 3.6) File Edit Search Source Run Debug Consoles Projects Tools View Help
File Edit Search Source Run Debug Consoles Projects Tools View HelpP
Editor- D:python_dass11forloop1.pPY
Cy ifelsestat..pyE untited1.py grade.py
Editor D:python dass_11nested while.py nested if.py while.py nested while.p
while.py nesi| 1# iist of.nunbers
untitled1.py grade.py nestedif.py
temp-py if
else stat..py s
2 numbers =
[6, 5, 3, 8, 4, 2, 5, 4, 11]
1 i = 1
4 # Variable tO store the sun
2j 5
Sum =
while 4:
while j < 8:
print(i, ",", i
4 i terate over the tist
8 for val in numbers:
9 sum = sum+val
LO
11
12 print(" The sum is", um)
Output: Output:
Python console
Python console
Console 1/A Console2/A Console 1/A
Python 3.6.5 |Anaconda, Inc.| (default, Mar 29 2018, 13:32:41) [MSC v.1900 64 bit
(AMD64) ]
Type "copyright", "credits" or "license" for more information.
Python 3.6.5 Anaconda, Inc.| (default, Mar 29 2018, 13:32:41) [MSC v.1900 64 bit
(AMD64)1
Type "copyright", "credits" or "license" for more information .
IPython 6.4.0 An enhanced Interactive Python.
IPython 6.4.0 -- An enhanced Interactive Python.
In [1]:
In 1: runfile( "b:/python class/nested while.py', wdir='D:/python class')
1 In [1]: runfile("D:/python_ class / for loop1.py', wdir='D:/python_ class')
The sum is 48
In [2]:
FOR LOODP NESTED FoR LooÞP
The for loop in Python is used to iterate over a sequence (list, tuple, string) or other objects. Iterating y contain arnotherloop in
its body. This is
called nested loop. But in nested loop. the inne
e
over a sequence is called traversal. loop must terminate before the outer loop. for loop can be nested within another for loop.
Syntax:
for each item
Example 9: Nested for loop.
in sequence
for <val> in <sequence>: Spyder (Python 3.6)
Body of for File Edit Search Source Run Debug Consoles Projects Tools View Help
es
Last i
Here, val is the variable that takes the value of the item inside the
reached
sequence on each iteration. Editor D:Python class_11nested forloop-pY
No
Loop continues until we reach the last item in the sequence. The body of
for loop is separated from the rest of the code using indentation.
statment3.py E3
1 for outer in range (6,10,4):
for inner in range(1,outer,2):
print (outer, inner)
nested for loop-py 3
Bodyoffor
Exit loop
ig. 3 Flowchart of for Loo
Conditions and Loops in Python
256 257
o m p u t e r
Applications
i o n s
andL

6. cONTINUE STATEMENT
Output: Enter loop
The continue statement is used to skip the rest of the code inside a loop
for the current iteration only. Loop does not terminate but continues on
n 1: runfile( D:/python lass /nested for loop.py', wdir='D:/python class")
Test
False
expression of
oop
6 3 with the next iteration.
Syntax:
True
Continue
JUMP STATEMENTSs BREAKANDCONTINUE
Yes
Python offers two jump statements to be used within loops tojump out of loop-iterations. These
break and continue statements.
s. These are Example 11: Program using continue Statement. Continue?
Spyder(Python3.6)
File Edit Search Source Run Debug Consoles Projects Tools View Help
Enter loop |No
Exit
loOP
THE BREAK STATEMENT Test Remaining8
False Editor-D:python cass 11continuel.py
body ofloop
Ihe break statement terminates the loop containing it. Control of
the program flows to the statement immediately after the body of
the loop.
expression of
looP
19y gradepy nestedfpy3 while.py3 nested wnie.py PYunon.py or oop1.g
Fig. 5 Flowchart of Continue
2 for val in "string":
True 3 if val == "i":
4 continue
If break statement is inside a nested loop (loop inside another
loop). break will terminate the innermost loop.
5 print(val1)
Yes
Break? 7 print(The end")
Syntax:
No
break
Output:
Exit
loop
Remaining
bodyofloop Tn [4]: runfile( 'D: /python_ class /continue1 .Py', wdir='D: /python_ class ")
Fig. 4 Flowchart of break
Example 10:
Theend
Spyder (Python 3.6)
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Example 12: Program to illustrate the difference between break and continue statement.
Spyder (Python3.6)
File Edit Search Source Run Debug Consoles Projects Tools View HelpP
Editor D:python dass_1iibreaki.py
at-py untitied.Py gade.py nested f-py while.py nested while.py Pyon
1 for val in "string" : Editor-D:ythonclass_11statment3.py
if val == "i": statment3.py
break 1 #break condit ion
print(val) 2print("the loop with break statement produces output as:
3 for i in range(1,10):
if ik2==0:
6 print(The end") 4
break
B else:
print(i
8 #cont inue condtit ion
Output: 9print("the loop with continue statement produces output as: ")
18 for i in range(1,10):
In [2]: runfile( D:/python_ class (break1.py', wdir='D:/python_ class ')
if ix2==0:
12 continue
t
L3 else:
4 print(i)
The end
Computer
plication Conditions and Loops in Python
259
258

7. Output: Ans. Ans. it will calculate square of numbers
enter an integer3
lass/statment3.py', wdir='D:/python
class
")
In [7]: runfile( D. /python
the loop with break statement produces output as
the loop with continue statement produces output as Q4. Find the output offollowing code.
=1
*2
1= 3 Q8. Write a program to check whether given numberis
even or odd.
sum=
ANS.
number=int (input ("enter any e"))
for i in (x.y.2): number$2==0:
if (isinstancei, int): print
(number,"i an even
nher")|
Lets Summarise Sum =sum+i print (number, "1s an dd nunber ")
print fsum)
Output:
Python supports selection orconditional statements.
There are three types ofstatements in python, namely emply statements, simple statements. compound statements.
The iteration constructs mean repetition of a set-of-Stalements depending upon a condition till the time a condition is true (or
Ans. enter any nunber12
n even nunber
Q5. What gets printed?
false depending upon the loop), a set-of-statements are repeated again and again. Q9. Program to print whetlher a given character is an
if x>3:
uppercase or a lowercase character or a digit or any
other character.
A Compound statement represents a group of statements executed as a unit.
if x>4:
------~----- -----*- printA",end=" ") AnS.
character iiput"entei d
ligL cia ")
Character>*' 11d charaCter<='2':
else:
Glossary haTActe .tLacter")
charact
printB".end="*")
, .
prnt("yo 7t
charactetx"i ' ai character<'':
P a t e i r u ilg
if(x!=0):
. Endless Loop: A loop that never ends or called infinite loop.
printc",end="*)
2 Empty Statement: A statement that appears in the code but does nothing.
3. Body: The blocks of statement in a compound statenments that follows the header.
print( D"
Ans. =RESTART:
D/python class/code3.py
Output:
********** RE.TART: D:/pytho ciess11/Gutputi.py **muanuzsa
4. Nested Loop: A loop contains another loop inside its body. D > ***
A iPytnon_ Class1/outputl.pY ***=e*au
5. teration: set of instructions to be performed repeatedly.
Q6. What gets printed? You entered i7t
6. Entry-controlled loop: that control over entry in the loop in the form of test condition.
temp=int(input(""enter temperature")
if temp<32:
************* RE3TART: D:/PYthon ciass11/output!.py ****aon**u
* ***** atacte?
print(ice") nrer . r a t e c P T O n Ca35 cutputi.Fy w*m*=n*a*me
Solved Questions elif temp<212: ya entered an uyperca3e chiaracter
*aaauw=mvananazanz RESTART: D:/python class
i/Gutpatl.9¥****
entez a single characer:®
p C i a Charucter
print"water")
else:
Q1. Can you use one or more loop inside any another while, for or do.... while loop? print("steam")
Ans. Yes. Q10. Program to calculate the factorial of a number
Ans. enter temperature 37
Ans. nu1nt(input(enter a nnbe: "))
water
Q2 Write the name of loop which executes a sequence of statements multiple times and abbreviates the coue
manages the loop variable.
Tacc
>>>
acsnum:
"**
Ans. or-ioop. tact"
97 What would the follow ing code print if you input
the value 3?
a
printIactoti e Iact)
Q3. What is the output ofthe following?
i =0 n=intinput("enter an integer") Output:
while i < 3: if n<l: enter d unoEt
printii) print(invalid value")
else:
fori in range(1,n+1)
printi*i)
else: a c t o d l oL nnDer izU
Iactorial or numbeT 120
printi) Iactor1ai ot number 5040
260
mnuter Applicatio Conditions and Loops in Python

8. print("Input lengths of the triangie sides: ")
X = int (input ("x: "))
Y int (input("Y: "))
Z =
int (input("z: "))
Q11. Program to Reverse a Given Number Ans.
Ans. n=int (input("Enter number: "})
rev=0
.e(n>0)
dig=n$10
rev=rev*10+dig
n=n//10
print("ECquiiaterai triangle")
if x != y != z:
print("Reverse of the numioer: ", rev) print ("Scalene triarngie"))
Output: print("isosceles triangle")
Enter number: 123
Reverse of the number: 321
Output:
==== RESTART: D:/python class _11/pattern 3
Input engths of the triangle sides:
x:10
Y: 15
2: 19
Scalene triangle
Q12. Program to Print an Inverted Star Pattern.
n=int(input("Enter number of rows: "))
or i range (n,0,-1):
print (n-i) *
+ i * 'a'
Ans.
Output:
Enter number of rows: 4
==u====== RESTART: D:/python class 11/pattern
Input iengths of the triangle sides:
10
y: 10
2:
Equilatera! triangle
>>>
* * *
10
=== RESTART: D:/python class_1/pattern
Q13. Write a program to input 3 sides ofa triangle and
|Input 1engths of the triangle sides:
10
x
10
print whether and print whether it is an equilateral,
scalene or isosceles triangle.
Y:
z: 15
isosceles triangle