Download Python Programming, Liang Chapters 1-6 . and more Summaries Computer Science in PDF only on Docsity!
Python Programming, Liang
Chapters 1- 6.
unicode (def, example) - ANSWERhexadecimal system for all international characters, includes ASCII system for all English characters and symbols i.e. print("\u6B22 \u8FCE \u03b1") communication devices - ANSWERi.e. modems, network interface cards, DSL, LAN byte, bit, mega-, giga-, kilo- tera- - ANSWERbit = minimum unit of storage (i.e. binary 1 or 0) 1 byte = 8 bits kilobyte = 1000 bytes megabyte = 1 million bytes gigabyte = 1 billion bytes terabyte - 1 trillion bytes disks' storage space - ANSWERused for permanently storing data, 200- 800 gigabytes can be stored types of languages (3) - ANSWERmachine language - binary assembly language - developed to make programming easier, uses words high-level language- platform-independent language using statements (i.e. Ada, Pascal, BASIC)
OS techniques - ANSWERmultiprogramming: allows multiple programs to run simultaneously by sharing the same CPU multithreading: allows a single program to execute tasks at the same time multiprocessing / parallel processing: uses 2+ processors together to perform subtasks concurrently ''' ''' - ANSWERencloses a paragraph comment code to display addition, subtraction, multiplication and division of two numbers - ANSWERprint(x + y) print(x - y) print(x * y) print(x / y)
- ANSWERline comment, used for comments for documentation for
readers, ignored by Python runtime error - ANSWERoccurs when programmer gives Python something too hard to calculate (i.e. division by zero, int vs. string), program won't run logic error - ANSWERerror in math or other thing that causes the program to not function properly command to run another Python source file, "filename" - ANSWERpython filename.py
- may contain letters, numbers and/or underscores
- cannot start with a digit but may use digit
- cannot be a keyword but may contain keyword cannot contain key symbols
- CAN start with underscore tips for creating identifiers - ANSWERbe descriptive, use camelCase for more than one word, lowercase for variables, upper case for constants variables - ANSWERnames that reference values stored in memory (i.e. identifiers whose values are not constant) code for displaying area and radius after user inputted area and radius was calculated - ANSWERprint("The area is", area, "for radius", radius) easier way to code k = j = k i = j - ANSWERi = j = k = 1 scope of a variable - ANSWERpart of the program where the variable can be referenced simultaneous assignment of x = 1, y = 2, z = 3 - ANSWERx, y, z = 1, 2, 3 simple code for how to swap values x and y - ANSWERx, y = y, x
long code for how to swap values x and y (using temp) - ANSWERx = 1 y = temp = x x = y y = temp input statement for asking user to enter three numbers x y and z - ANSWERx, y, z = eval(input("Enter three numbers separated by commas.")) #input must be separated by commas types of division (2) - ANSWER/ float division: to get a decimal (even if operands are integers and even if there are other math operators!!) // integer division: to get an integer (no rounding; all .decimals are stripped off) types of numeric data (2) - ANSWERinteger: 1, 73, - 12 float: 1.0, 23.5, - 12. unary versus binary operators, examples - ANSWERunary: only one number it it operates on (-5) binary: two numbers it operates on (5-4) code for determining whether x is even or odd number - ANSWERx%2 =0 if even, x%2 = 1 if odd
int(x) 5 2)Used to convert str to int int(input(x)) round - ANSWERrounds a number to the nearest whole value, if it is equally close to 2 integers, the even one is returned x = 4. round(x) 4 eval vs. int - ANSWERsame for integer with quotes, must be eval for float in quotes and math in quotes, must be int if it starts with 0's in quotes int("34") = eval("34") int("3.4") does not work, eval("3.4") does int ("3 + 4") does not work, eval ("3 + 4") does BUT int("003") does work and eval("003") doesn't. code for how to convert to two decimal places for $ amounts - ANSWERint(x
- / 100.0) UNIX epoch - ANSWERimport time time.time()
current time in seconds since 00:00:00 on 1/1/1970 (when UNIX Os was introduced) software development process (7) - ANSWERRequirements specification (to run the program, the system needs xyz capability) System analysis (identify input and output) System design (IPO steps of program, #) Implementation (coding, self-testing, debugging) Testing (independent team) Deployment Maintenance formula for monthly payment of loan - ANSWERmonthlyPayment = loanAmount * monthlyInterestRate / (1-1 / (1 + monthlyInterestRate) ** (numberOfYears * 12)) totalPayment = monthlyPayment * numberOfYears * 12 code for square root of a - ANSWERa ** 0. code for calculating distance between two points - ANSWERdistance = ((x1 - x2) * x1-x2)) + ((y1 - y2) * (y1-y2)) ** 0. code to find absolute value of z - ANSWERabs(x)
how to get absolute value for integer x as a float - ANSWERmath.fabs(x) how to round x up to its nearest integer - ANSWERmath.ceil(x) how to round x down to it nearest integer - ANSWERmath.floor(x) how to get the natural logarithm of x - ANSWERmath.log(x) how to get the square root of x - ANSWERmath.sqr(x) how to get logarithm of x for specified base - ANSWERmath.log(x, base) how to get the sin, cosine and tangent of (x,x) - ANSWERmath.sin(x) math.cos(x) math.tan(x) how to convert angle x from radians to degrees, from degrees to radians - ANSWERmath.degrees(x) math.radians(x) ' ' versus '' '' - ANSWERboth used to convey a string conventionally '' '' used for >1 character ' ' used for single character or empty string because it is easier to convert to other languages
function for returning ASCII code for character a - ANSWERch = 'a' ord(ch) or ord('a') function for returning character represented by ASCII code 'x' - ANSWERchr(x) how to find uppercase representation of any lowercase letter - ANSWERoffset = ord('a') - ord('A') lowercaseletter = 'h' uppercaseletter = chr(ord(lowercaseletter) - offset) uppercaseLetter (difference is always 32) escape sequence (8) - ANSWER\n new line, line break or EOL \f forces printer to print from next page \r moves cursor to first position on same line \b backspace \t tab \ backslash \' single quote
remainingamount = int(x * 100) numberofDollars = remainingamount // 100 remainingamount = remainingamount % 100 numberofQuarters = remainingamount // 25 remainingamount = remainingamount % 25 numberofdimes = remainingamount // 10 remainingamount = remainingamount % 10 numberofnickels = remainingamount // 5 remainingamount = remainingamount % 5 numberofpennies = remainingamount how to get id, type / class of object x - ANSWERid(x) type(x) change case for string x - ANSWERx = "string" y = x.lower() or y = x.upper() y
how to remove white space for string "\t string \n" - ANSWERx = "\t string \n" y = x.strip() y format the number 1.2345 to show only two decimals and have three blank spaces in front of it - ANSWERprint(format(1.2345, "3.2f") output for print(format(1.23456, ".3f") output for print(format(1.2, "10.3f") - ANSWER1.
output for print(format(57. - ANSWER convert 0.53467 to display as percent - ANSWERprint(format(0.53467, ".2%")) show 0.9812 as a percent with one space in front of it - ANSWERprint(format(0.9812, "7.2%")) show 45.678 left justified with one decimal place - ANSWERprint(format(45.678, "<.2f")) #this will also round it show hexadecimal value of 12345 with 10 spaces in front - ANSWERprint(format(12345, "10x"))
output for 1 + 1 == 2 - ANSWERTrue how to check whether a number n is even - ANSWERn % 2 == 0 how to check whether a number is a multiple of x - ANSWERn % x == 0 go to next line - ANSWER elif is the same as (structure) - ANSWERelse: if: condition \ - ANSWERgo to next line or ignore next item logical operators - ANSWERand, or, not not x and y is the same as - ANSWERnot x or y not (x or y) is the same as - ANSWERnot x and not y leap year - ANSWERleap year % 4 == 0 another way to say if x > 0: y = 1
else: y = - 1 - ANSWERy = 1 if x > 0 else - 1 division - ANSWER/ how to determine whether given point z is inside a circle - ANSWERif distance from z to center of circle is > radius of circle output for print("item", end = '') print ("seconditem") - ANSWERitem seconditem speed of CPU measured in ... - ANSWERmegahertz (1 million pulses per second) NIC device - ANSWERused to connect computer to local area network (LAN) to start python from command prompt, use command - ANSWERpython to run python file script named t.py, use the command - ANSWERpython t.py eval(1 + 2) - ANSWERerror eval("1 + 2") - ANSWER 3
syntax for simple for loop - ANSWERfor value in sequence: Statements basic parts of while loop - ANSWERwhile continuation condition: Statements Additional statements for controlling the loop sentinel value - ANSWERadditional x = 0, x = x + 1 type value that signifies the end of the loop, common technique for controlling the loop, should never be floating point values syntax of while loop with sentinel value - ANSWERx = eval(input("Enter x.")) sum = 0 while x != 0: sum += x x = eval(input("Enter x.")) print ("The sum is," sum) input redirection - ANSWERstoring data in text file and running it from python how to run program for text file on Python file python.py - ANSWERpython python.py < input.txt
output redirection - ANSWERsend output to file instead of displaying it on Python screen how to send py file text.py to outside text - ANSWERpython text.py > output.txt output for for v in range (4,8) print(v) - ANSWER 4 5 6 7 8 output for for v in range(3, 9, 2) print(v) - ANSWER 3 5 7 output for for i in range(1,5): j = 0 while j < 1: print(j, end = "")
