Unit 4 If else return user input strings Special thanks to Scott Shawcroft Ryan Tucker and Paul Beck for their work on these slides Except where otherwise noted this work is licensed under http creativecommons org licenses by nc sa 3 0 Math commands from math import Function name abs value Description Description absolute value Constant e ceil value rounds up pi 3 1415926 cos value cosine in radians degrees value convert radians to degrees floor value rounds down log value base logarithm in any base log10 value logarithm base 10 2 7182818 max value1 value2 larger of two or more values min value1 value2 smaller of two or more values radians value convert degrees to radians round value nearest whole number sin value sine in radians sqrt value square root tan value tangent 2 Returning values def name parameters statements return expression Python doesn t require you to declare that your function returns a value you just return something at its end def ftoc temp tempc 5 0 9 0 temp 32 return tempc ftoc 98 6 37 0 3 input input Reads a string from the user s keyboard reads and returns an entire line of input name input Howdy What s yer name Howdy What s yer name Paris Hilton name Paris Hilton NOTE Older v2 x versions of Python handled user input differently These slides are about the modern v3 x of Python and above 4 input to read numbers cast input result to an int or float If the user does not type a number an error occurs Example age int input How old are you print Your age is age print 65 age years to retirement Output How old are you 53 Your age is 53 12 years to retirement 5 if if condition statements Example gpa float input What is your GPA if gpa 2 0 print Your application is accepted 6 if else if condition statements elif condition statements else statements Example gpa float input What is your GPA if gpa 3 5 print You have qualified for the honor roll elif gpa 2 0 print Welcome to Mars University else print Your application is denied 7 if in if value in sequence statements The sequence can be a range string tuple or list seen later Examples x 3 if x in range 0 10 print x is between 0 and 9 letter input What is your favorite letter if letter in aeiou print It is a vowel 8 Logical Operators Operator Meaning Example Result equals 1 1 2 True does not equal 3 2 2 5 True less than 10 5 False greater than 10 5 True less than or equal to 126 100 False greater than or equal to 5 0 5 0 True Operator Example Result and 2 3 and 1 5 False or 2 3 or True not 1 5 not 2 3 True 9 Exercise Write a program that reads two employees hours and displays each employee s total and the overall total Cap each day at 8 hours Employee 1 How many days 3 Hours 6 Hours 12 Hours 5 Employee 1 s total hours 19 6 33 day Employee 2 How many days 2 Hours 11 Hours 6 Employee 2 s total hours 14 7 00 day Total hours for both 33 10 Strings index 0 1 2 3 4 5 6 7 or 8 P 7 6 5 D 4 i 3 d 2 d 1 y character Accessing character s variable index variable index1 index2 index2 exclusive index1 or index2 can be omitted goes to end of string name P Diddy name 0 P name 7 y name 1 y name 3 6 Did name 3 Diddy name 2 P Did 11 String Methods Java Python length len str startsWith endsWith startswith endswith toLowerCase toUpperCase upper lower isupper islower capitalize swapcase indexOf find trim strip name Martin Douglas Stepp name upper MARTIN DOUGLAS STEPP name lower startswith martin True len name 20 12 for Loops and Strings A for loop can examine each character in a string in order for name in string statements for c in booyah print c b o o y a h 13 Formatting Text format string parameter parameter Placeholders insert formatted values into a string d f s an integer a real number a string an integer 8 characters wide right aligned an integer 8 characters wide padding with 0s an integer 8 characters wide left aligned a real number 12 characters wide a real number 4 characters after decimal a real number 6 total characters wide 2 after decimal 8d 08d 8d 12f 4f 6 2f x 3 y 3 14159 z hello print 8s 04d is close to 3f z x y hello 0003 is close to 3 142 14 Strings and Integers ord text Converts a string into a number ord a is 97 ord b is 98 Uses standard mappings such as ASCII and Unicode chr number Converts a number into a string chr 97 is a chr 99 is c 15 Basic cryptography Rotation cipher shift each letter by some fixed amount Caesar cipher shift each letter forward by 3 the cake is a lie becomes wkh fdnh lv d olh Substitution cipher transform each letter into another not a linear shift uses some kind of letter mapping similar to cryptogram or cryptoquip games in newspaper 16 Exercise Write a program that encrypts a secret message with a Caesar cipher shifting the letters of the message by 3 e g Attack when rotated by 1 becomes cwwcfn If you have time make the program able to undo the cipher Can you write a function that works for a substitution cipher 17
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