Ch 1. Introduction Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.
Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.
-
Upload
lee-lawrence -
Category
Documents
-
view
220 -
download
0
Transcript of Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.
![Page 1: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/1.jpg)
Chapter 9 IF Statement
Dr. Bernard Chen Ph.D.University of Central Arkansas
Spring 2012
![Page 2: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/2.jpg)
Outline
Logic expression General concept behind the Python
statement syntax IF statement
![Page 3: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/3.jpg)
Some Logic Expression
Computer only understand ‘1’ and ‘0’
In computer logic: 1: true 0: false
![Page 4: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/4.jpg)
Some Logic Expression
Equal: “==”
NOT Equal: “!=”
Greater: “>”, “>=”
Less than: “<”, “<=”
![Page 5: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/5.jpg)
Some Logic Expression example
>>> a=10>>> b=10>>> a==b
>>> a=10>>> b=5>>> a==b
![Page 6: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/6.jpg)
Some Logic Expression example
>>> a=10>>> b=10>>> a!=b
>>> a=10>>> b=5>>> a!=b
![Page 7: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/7.jpg)
Some Logic Expression example
>>> a=10>>> b=10>>> a>=b
>>> a=10>>> b=5>>> a<b
![Page 8: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/8.jpg)
Outline
Logic expression General concept behind the Python
statement syntax IF statement
![Page 9: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/9.jpg)
Python’s Syntax
In general, Python has a simple syntax: Block and statement boundaries are
detected automatically: python use indention of statement under a header to group the statement
Header --- ‘:’
![Page 10: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/10.jpg)
Outline
Logic expression General concept behind the Python
statement syntax IF statement
Simple If statement If... else statement If… else if … else statement
![Page 11: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/11.jpg)
If Statement
The main statement used for selecting from alternative actions based on test results
It’s the primary selection tool in Python and represents the Logic process
![Page 12: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/12.jpg)
Simple If statement
It takes the form of an if test
if <test>: <statement>
![Page 13: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/13.jpg)
Simple If statement if 4>3: print “it is true that 4>3”
if 1: print “true”
a=10 if a==10:
print “a=10”
![Page 14: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/14.jpg)
Truth Statement
In Python: True means any nonzero number or
nonempty object False means not true: a zero number
of empty object
![Page 15: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/15.jpg)
If Statement “login” example
![Page 16: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/16.jpg)
If... else statement
It takes the form of an if test, and ends with an optional else block
if <test>: <statement1> else: <statement2>
![Page 17: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/17.jpg)
If Statement “login” example
![Page 18: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/18.jpg)
If... else statement
>>> a=10>>> b=5>>> if a>b: print “a is larger” else: print “b is larger”
![Page 19: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/19.jpg)
If... else statement a=10 if a==10:
print “a=10” else: print “a is not equal to 10”
(also try >, < )
![Page 20: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/20.jpg)
If… else if … else statement It takes the form of an if test, followed
by one or more optional elif tests, and ends with an optional else block
if <test1>: <statement1>elif <test2>:
<statement2>else: <statement3>
![Page 21: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/21.jpg)
If… else if … else statement
a=10 if a>10:
print “a > 10” elif a==10:
print “a = 10” else: print “a < 10”
![Page 22: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/22.jpg)
If… else if … else statement examplenumber = 23guess = int(raw_input('Enter an integer : '))
if guess == number:print 'Congratulations, you guessed it.'print "(but you do not win any prizes!)"
elif guess < number:print 'No, it is a little higher than that'
else:print 'No, it is a little lower than that'
![Page 23: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/23.jpg)
In class practiceimport randomnumber=random.randint(1,5)
guess = int(raw_input('Enter an integer : '))
if guess == number:print 'Congratulations, you guessed it.'print "(but you do not win any prizes!)"
elif guess < number:print 'No, it is a little higher than that'
else:print 'No, it is a little lower than that'
print 'The answer is:',number
![Page 24: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/24.jpg)
Some More Logic Expression And (True if both are true)
Examples:>>> 5>4 and 8>7True>>> 5>4 and 8>9False
A B A and B
0 0 0
0 1 0
1 0 0
1 1 1
![Page 25: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/25.jpg)
Exampletemp=int(raw_input("Please enter today's tempeture:"))rain=int(raw_input("Is is raining? 1:yes, 0:no"))
if temp>86 and rain==0: print "Today is a hot sunny day"elif temp>86 and rain==1: print "Today is a hot raining day"elif temp<32 and rain==0: print "Today is a cold sunny day"elif temp<32 and rain==1: print "Today is a cold raining day"else: print "Today's weather is not special"
![Page 26: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/26.jpg)
Some More Logic Expression Or(True if either one is
true)
Examples:>>> 5>4 or 8>7True>>> 5>4 or 8>9True
A B A or B
0 0 0
0 1 1
1 0 1
1 1 1
![Page 27: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/27.jpg)
Example
a=10b=20
if a%2==0 and b%2==0: print "Both a and b are even numbers"elif a%2==0 or b%2==0: print "Either a or b is an even number"else: print "Both a and b are odd numbers"
![Page 28: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/28.jpg)
Nested IF statement
Sometimes you may want to check one condition after another condition. In such situation, we call it “Nested IF Statement”
The Code would looks something like:
![Page 29: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/29.jpg)
Nested IF statement
![Page 30: Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012.](https://reader035.fdocuments.us/reader035/viewer/2022062407/56649dd15503460f94ac7a45/html5/thumbnails/30.jpg)
Example:deposit=int(raw_input('Clerk: How much do you want to deposit? '))
if deposit > 100000: print "Wow, that's a lot of money" if deposit < 500000: print "I need to call my manager" elif deposit < 1000000: print "Let me open an VIP room for you" else: print "Can you merry me?"
elif deposit > 1000: print "Sure, let me do it right now, do you want to consider a CD"elif deposit > 1: print "Sure, let me do it right now"else: print "Are you kidding me, I am busy right now..."