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Sophia Whitehead
5 years ago
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1 ! " if " %&% ifelse!()!() " &% ifelif-else "*+ % + & "*- +bool (.%) "%.* *%!!%.* *%* 0* **!! 0.*%* %. *% % % % +*.* **% *

2 3 4! * convert.py A program to convert Celsius temps to Fahrenheit by: Susan Computewell celsius = input("what is the Celsius temperature? ") fahrenheit = * celsius + 32 print "The temperature is" fahrenheit "degrees Fahrenheit." 3 %%* % % %+!67 4%7 4% %%! main() 5 () *68 * **967 % **97 % "% % " **! 6 7 convert2.py A program to convert Celsius temps to Fahrenheit. This version issues heat and cold warnings. celsius = input("what is the Celsius temperature? ") fahrenheit = * celsius + 32 print "The temperature is" fahrenheit "degrees fahrenheit." if fahrenheit >= 90: print "Its really hot out there be careful!" if fahrenheit <= 30: print "Brrrrr. Be sure to dress warmly" main()

3 "if if <condition>: <body> ".* if "*if 4! *.* + + ** :+ "*if + + *if "&% 4 4 0::; <expr> <relop> <expr> >> 9> 9 => 3 3. > 2.?. 9? <. 5

4 4 <*==*. = *.* *. : = = *& *%& ( - * ) *2? - 0-+!!*( )*( ) 7 * -*bool -!** True False >>> 3 < 4 True >>> 3 * 4 < False >>> "hello" == "hello" True >>> "Hello" < "hello" True 2+ "!%* "* "* %% & 2+ 0%% %main() *!* %!

5 2+?%% % %+= & main if <condition>: main() 2+ 0!! name * >>> import math >>> math. name math 2+ 0 name! math 0!* name main 2 >>> name main 2+ "* %! name %!* 0*%! main 0 ** if name == main : main() B!%= 5 3 :. %* quadratic.py A program that computes the real roots of a quadratic equation. Illustrates use of the math library. Note: This program crashes if the equation has no real roots. import math Makes the math library available. print "This program finds the real solutions to a quadratic" print a b c = input("please enter the coefficients (a b c): ") discroot = math.sqrt(b * b - 4 * a * c) root = (-b + discroot) (2 * a) root2 = (-b - discroot) (2 * a) print print "The solutions are:" root root2 % &@7 :.*! This program finds the real solutions to a quadratic Please enter the coefficients (a b c): 2 Traceback (most recent call last): File "C:\Documents and Settings\Terry\My Documents\Teaching\W04\CS 20\Textbook\code\chapter3\quadratic.py" line 2 in -toplevelmain() File "C:\Documents and Settings\Terry\My Documents\Teaching\W04\CS 20\Textbook\code\chapter3\quadratic.py" line 4 in main discroot = math.sqrt(b * b - 4 * a * c) ValueError: math domain error main() 6 7

6 0:*C * quadratic2.py A program that computes the real roots of a quadratic equation. Bad version using a simple if to avoid program crash import math print "This program finds the real solutions to a quadratic\n" a b c = input("please enter the coefficients (a b c): ") discrim = b * b - 4 * a * c if discrim >= 0: discroot = math.sqrt(discrim) root = (-b + discroot) (2 * a) root2 = (-b - discroot) (2 * a) print "\nthe solutions are:" root root2 0* ( &)::!* % 3:* 0 % %;C0 %; This program finds the real solutions to a quadratic Please enter the coefficients (a b c): >>> "%! %D:% %%% = 0if if discrim < 0: print "The equation has no real roots!" "%:*% 0! %%+! (*discrim >= 0 discrim < 0*!!) %&% else if "if-else if <condition>: <statements> <statements>

7 0* *!* if + ** else + *% if-else +** + quadratic3.py A program that computes the real roots of a quadratic equation. Illustrates use of a two-way decision import math print "This program finds the real solutions to a quadratic\n" a b c = input("please enter the coefficients (a b c): ") discrim = b * b - 4 * a * c if discrim < 0: print "\nthe equation has no real roots!" discroot = math.sqrt(b * b - 4 * a * c) root = (-b + discroot) (2 * a) root2 = (-b - discroot) (2 * a) print "\nthe solutions are:" root root2 main() 5 >>> This program finds the real solutions to a quadratic Please enter the coefficients (a b c): 2 The equation has no real roots! >>> This program finds the real solutions to a quadratic Please enter the coefficients (a b c): The solutions are: A&0 "%.:= This program finds the real solutions to a quadratic Please enter the coefficients (a b c): 2 The solutions are: A&0 0 * *:: : %= % +7 ::%&% = A&0 Check the value of discrim when < 0: handle the case of no roots when = 0: handle the case of a double root when > 0: handle the case of two distinct roots 0%%*& *

8 A&0 A&0 if discrim < 0: print "Equation has no real roots" if discrim == 0: root = -b (2 * a) print "There is a double root at" root Do stuff for two roots A&0 *%:*!& % "ifelse %*!= "! else *%if elif A&0 if <condition>: <case statements> elif <condition2>: <case2 statements> elif <condition3>: <case3 statements> <default statements> A&0 "*** +!:! : *** * + +* if-elif-else *else * A&0 "else * elsed: %+ 5 5

9 A&0 quadratic4.py A program that computes the real roots of a quadratic equation. Illustrates use of a multi-way decision import math print "This program finds the real solutions to a quadratic\n" a b c = input("please enter the coefficients (a b c): ") discrim = b * b - 4 * a * c if discrim < 0: print "\nthe equation has no real roots!" elif discrim == 0: root = -b (2 * a) print "\nthere is a double root at" root discroot = math.sqrt(b * b - 4 * a * c) root = (-b + discroot) (2 * a) root2 = (-b - discroot) (2 * a) print "\nthe solutions are:" root root2 6. %!:.*!! & "* 7.+%: * sqrt *%:*!% * 2 *. (.!!%:%! %.) discrt = othersqrt(b*b - 4*a*c) if discrt < 0: print "No real roots.... :* *%! %+! " % % % * % "! +: quadratic5.py A program that computes the real roots of a quadratic equation. Illustrates exception handling to avoid crash on bad inputs import math print "This program finds the real solutions to a quadratic\n" try: a b c = input("please enter the coefficients (a b c): ") discroot = math.sqrt(b * b - 4 * a * c) root = (-b + discroot) (2 * a) root2 = (-b - discroot) (2 * a) print "\nthe solutions are:" root root2 except ValueError: print "\nno real roots" 6

10 "try *% * try: <body> except <ErrorType>: <handler> 0try + *+ *try except *%+ :*+% ** + " %! Traceback (most recent call last): File "C:\Documents and Settings\Terry\My Documents\Teaching\W04\CS20\Textbook\code\chapter3\quadratic.py" line 2 in -toplevelmain() File "C:\Documents and Settings\Terry\My Documents\Teaching\W04\CS 20\Textbook\code\chapter3\quadratic.py" line 4 in main discroot = math.sqrt(b * b - 4 * a * c) ValueError: math domain error "EValueError: math domain errorf** CD% This program finds the real solutions to a quadratic Please enter the coefficients (a b c): No real roots * + "try except :*!* *+ *. *( unpack tuple of wrong sizef) * *(NameError)!+(TypeError) try! except 5 quadratic6.py A program that computes the real roots of a quadratic equation. Illustrates robust exception handling to avoid crash on bad inputs import math print "This program finds the real solutions to a quadratic\n" try: a b c = input("please enter the coefficients (a b c): ") discroot = math.sqrt(b * b - 4 * a * c) root = (-b + discroot) (2 * a) root2 = (-b - discroot) (2 * a) print "\nthe solutions are:" root root2 except ValueError excobj: msg = str(excobj) if msg == "math domain error": print "\nno Real Roots" elif msg == "unpack tuple of wrong size": print "\nyou didnt give me the right number of coefficients." print "\nsomething went wrong sorry!" 6 except NameError: print "\nyou didnt enter three numbers." except TypeError: print "\nyour inputs were not all numbers." except SyntaxError: print "\nyour input was not in the correct form. Missing comma(s) perhaps?" except: print "\nsomething went wrong sorry!" if name == main : main() 7 7

11 "excepts :elifs* %except : ** "except : else % * *%except *except %!* **%% *except % * + except ValueError excobj: msg = str(excobj) if msg == "math domain error": print "\nno Real Roots" elif msg == "unpack tuple of wrong size": print "\nyou didnt give me the right number of coefficients." print "\nsomething went wrong sorry!" A+*" <%%! %! "! % = % * * A+*" x x2 x3 = input("please enter three values: ") missing code sets max to the value of the largest print "The largest value is" max 2 "::&% %%+* *% max = x max = x2 max = x3 %%* *% =

12 2 3 :%+ if x >= x2 >= x3: max = x ; A %% % D.! !% %. 0+ * :; G %!== :!**.% %+ +;! ; 0D! *++%:% +9>++9>+ 0%= if x >= x2 and x >= x3: max = x elif x2 >= x and x2 >= x3: max = x2 max = x3 0D! % " 0%*%% *+**!!; 0%*- + ** H:= 0!*! %%x >= x2" ::x x2* + *% % x x3

13 " " if x >= x2: if x >= x3: max = x max = x3 if x2 >= x3: max = x2 else max = x3 ". ":+% * *! C%! *"* +**! ifelse!% C%%!; H: :%% -% *%!* ; : * 0* :: **!:! ::.. " max = x if x2 > max: max = x2 if x3 > max: max = x3 5

14 . "! * 0*% +* %+!. maxn.py Finds the maximum of a series of numbers n = input("how many numbers are there? ") Set max to be the first value max = input("enter a number >> ") Now compare the n- successive values for i in range(n-): x = input("enter a number >> ") if x > max: max = x 6 print "The largest value is" max 57 I &* max * x x2 x3 = input("please enter three values: ") print "The largest value is" max(x x2 x3) 3 " %! * *": :* % H*:* *!* * *%* :*%%! " *%* *? * * *+* %+*% : * 5 5

15 3!% *! *! ** *= * += "+ :%% % 5

Python Programming: An Introduction to Computer Science

Python Programming: An Introduction to Computer Science Chapter 7 Decision Structures Python Programming, 2/e 1 Objectives n To understand the programming pattern simple decision and its implementation