CS 112: Intro to Comp Prog

Transcription

1 CS 112: Intro to Comp Prog Data Types String In-detail Arithmetic Operators Variables Tipper Program Lab Assignment #1 Upcoming

2 Data Types <<Type>> <<conversion function>> Integer int () (aka Fixed-Point) { -1, 0, 7, 3, -5,...} Floating-Point float() (aka Decimal) {-0.25, 12.41, -0.1, 0, 5.0,...} String str() { Hello World, CS 112 Rocks!, Pineapple,...} Anything surrounded by quotes is considered a String

3 Strings Strings can be produced by using either or ' as long you stay consistent (i.e. what you start with you finish with). You can use the opposite quote inside without it affecting the syntax. Valid Strings: 'John said, Hi.' How's it going Invalid Strings Sally said, Good-bye. -closes early 'What's happening' -closes ' early Go away' -quote-type mismatch

4 Strings Inside a string you can specify a special character (\ backslash) to do a specific task \\ - print a backslash \' - print a single-quote \ - print a double-quote \n - newline \t - horizontal tab print "\tthis is an example\nof key \"special\' characters: /\\" Output: This is an example of key "special' characters: /\

5 String Functions Functions can be applied to strings to modify their format: upper() lower() swapcase() capitalize() title() strip() replace(<<old>>, <<new>> [, <<max>>]) "\thi there".upper() >>> HI THERE "\thi there".lower() >>> hi there "\thi there".swapcase() >>> HI THeRe "hi there".capitalize() >>>Hi there "\thi there".title() >>> Hi There "\thi there".strip() >>>hi there "\thi there".replace("hi","hello") >>> Hello there

6 String Operations + and * are operators with Strings...they can be used to combine or repeat a string + concatenation operator * repetition operator print Hi There, + John >>> Hi There, John print Beetlejuice * 3 >>> Beetlejuice Beetlejuice Beetlejuice print spider- + man >>> spider-man print what is + happening + my + friend? >>> what is happening my friend?

7 Arithmetic Operators Mathematical operators exists for both floats and ints + addition - subtraction * multiplication / division (for version less than 3: 1/2 = 0, v3+: 1/2 = 0.5) % modulus (returns the remainder) Functions exist as well that can be used with numbers : ceil(<<number>>) floor(<<number>>) fabs(<<number>>) round(<<number>> [, <<places>>])

8 Variables Variables denote blocks in memory that allow us (the programmers) to store and recall information at any point in the program. In order to create a variable we will need to specify a name and assign a value into it (whether it be text, numbers, etc.) this data specifies the variable's type. x = 5 - variable x is being created and assigned the integer value: 5 text = hello - variable text is being created and assigned the string value: hello data = variable data is being created and assigned the floating-point value: 8.1

9 Naming Variables Variable Names can only contain numbers, letters, and underscores Variable Name cannot start with a number Use meaningful names. Good Names first_name fifteenper bill LastName amt meters Bad Names (invalid & poorly named) 1stName fhdjsghg name#1 feet&inches purplepeopleeater

10 Summation Program x = int(raw_input("enter the first number : ")) # the raw_input reads in user input as a string, so it must be # converted to an int value using the conversion function # it is then stored in a new variable x y = int(raw_input("enter the second number : ")) # same as above except that we read in a second number storing # the value into a new variable y z = x + y # using the addition operator add the two values stored, and # store the result into a new variable z print "The sum of two numbers is " + str(z) # in order to combine the string with the value in z, # z must be converted to a string using the conversion function raw_input("\npress Enter to Exit")

11 Tipper Program Write a Tipper program where the user enters a restaurant bill total. The program should then display two amounts: a 15- percent tip and a 20-percent tip: Example Execution (Bolded and Italicized is user input) >>> tip.py Enter the restaurant bill total: Percent: 4.917, 20-Percent: ***Bonus: Round to nearest cent***

12 Tipper Solution # CS Sample Problem # Goal is to demonstrate key programming concepts # Program takes in a single decimal value and computes # two percentages of it bill = float(raw_input("enter the restaurant bill total: ")) # Gets the user's bill as a decimal value fifteenper = bill *.15 # computes a fifteen percent tip twentyper = bill *.2 # computes a twenty percent tip print "15-Percent: " + str(fifteenper) + ", 20-Percent: "+ str(twentyper) # outputs the result raw_input("\npress Enter to Exit")