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Chapter 9 IF Statement

Chapter 9 IF Statement. Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012. Outline. Logic expression General concept behind the Python statement syntax IF statement. Some Logic Expression. Computer only understand ‘1’ and ‘0’ In computer logic: 1: true 0: false.

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Chapter 9 IF Statement

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  1. Chapter 9 IF Statement Dr. Bernard Chen Ph.D. University of Central Arkansas Spring 2012

  2. Outline • Logic expression • General concept behind the Python statement syntax • IF statement

  3. Some Logic Expression • Computer only understand ‘1’ and ‘0’ • In computer logic: • 1: true • 0: false

  4. Some Logic Expression Equal: “==” NOT Equal: “!=” Greater: “>”, “>=” Less than: “<”, “<=”

  5. Some Logic Expression example >>> a=10 >>> b=10 >>> a==b >>> a=10 >>> b=5 >>> a==b

  6. Some Logic Expression example >>> a=10 >>> b=10 >>> a!=b >>> a=10 >>> b=5 >>> a!=b

  7. Some Logic Expression example >>> a=10 >>> b=10 >>> a>=b >>> a=10 >>> b=5 >>> a<b

  8. Outline • Logic expression • General concept behind the Python statement syntax • IF statement

  9. 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 --- ‘:’

  10. Outline • Logic expression • General concept behind the Python statement syntax • IF statement • Simple If statement • If... else statement • If… else if … else statement

  11. 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

  12. Simple If statement • It takes the form of an if test • if <test>: <statement>

  13. 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”

  14. Truth Statement • In Python: • True means any nonzero number or nonempty object • False means not true: a zero number of empty object

  15. If Statement “login” example

  16. If... else statement • It takes the form of an if test, and ends with an optional else block • if <test>: <statement1> else: <statement2>

  17. If Statement “login” example

  18. If... else statement >>> a=10 >>> b=5 >>> if a>b: print “a is larger” else: print “b is larger”

  19. If... else statement • a=10 • if a==10: print “a=10” else: print “a is not equal to 10” (also try >, < )

  20. 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>

  21. If… else if … else statement • a=10 • if a>10: print “a > 10” elif a==10: print “a = 10” else: print “a < 10”

  22. If… else if … else statement example number = 23 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'

  23. In class practice import random number=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

  24. Some More Logic Expression • And (True if both are true) Examples: >>> 5>4 and 8>7 True >>> 5>4 and 8>9 False

  25. Example temp=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"

  26. Some More Logic Expression • Or (True if either one is true) Examples: >>> 5>4 or 8>7 True >>> 5>4 or 8>9 True

  27. Example a=10 b=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"

  28. 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:

  29. Nested IF statement

  30. 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..."

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