The Islamic University of Gaza Faculty of Engineering Dept. of Computer Engineering Intro. To Computers (LNGG 1003) Lab 3 Variable and Data Type 2 Eng. Ibraheem Lubbad March 2, 2017
Python Lists: Lists are Python's compound data types. A list contains items separated by commas and enclosed within square brackets ([]). All the items belonging to a list can be of different data type. The values stored in a list can be accessed using the slice operator ([ ] and [:]) with indexes starting at 0 in the beginning of the list and working their way to end -1. Example 1: =["apple", "orange",100,25.5] [0] 'apple' >>> 3*items[:2] ['apple', 'orange', 'apple', 'orange', 'apple', 'orange'] [2]=items[2]+50 ['apple', 'orange', 150, 25.5] [0:2]=[20,30] # replace some elements [20, 30, 150, 25.5] [0:2]=[] # remove some elements [150, 25.5] [2:2]=[200,400] # insert some elements [150, 25.5, 200, 400] >>> del items[0] # delete element at index 0 from list [25.5, 200, 400].append("orange") # List.append(object) -- append object to end [25.5, 200, 400, 'orange'] >>> 200 in items # check existing item in list True >>> 200 not in items # check not existing item in list False
List Methods: name Description count ( value ) Returns the number of times a given value appears in the list Index( value) Returns the lowest index of a given element (value ) within the list extend(seq ) This method does not return any value but add the content sequence to existing list. insert(index,object) Inserts a new element (object) before the element at a given index. Increases the length of the list by one. append ( object ) Adds a new element (object) to the end of the list. remove(value) Removes the first occurrence (lowest index) of a given element (value) from the list. Produces an error if the element is not found. reverse() reverses the elements in the list. The list is modified sort Sorts the elements of the list in ascending order. The list is modified Python Tuples: A tuple is another sequence data type that is similar to the list. A tuple consists of a number of values separated by commas, tuples are enclosed within parentheses (). Tuples its read only, that s means are immutable. The main differences between lists and tuples are: Lists are enclosed in brackets ([ ]) and their elements and size can be changed, while tuples are enclosed in parentheses ( ( ) ) and cannot be updated.
Examples: Example 2: >>> t=("orange",55,3.5) >>> t[0] 'orange' >>> t[1:3] (55, 3.5) >>> t[-1] 3.5 >>> len(t) 3 >>> # Tuples may be nested >>> u=(t,(1,2,3)) >>> u (('orange', 55, 3.5), (1, 2, 3)) >>> len(u) 2 >>> # Tuples are immutable: >>> t[0]=100 # not allow to update tuple Traceback (most recent call last): File "<input>", line 1, in <module> TypeError: 'tuple' object does not support item assignment Tuple Methods: name count ( value ) Index( value) Description Returns the number of times a given value appears in the tuple Returns the lowest index of a given element (value ) within the tuple
Python Dictionary: Python's dictionaries are kind of hash table type consist of key-value pairs. A dictionary key can be almost any Python type, but are usually numbers or strings. A dictionary Values can be any arbitrary Python object. Dictionaries are enclosed by curly braces ({ }) and values can be assigned and accessed using square braces ([]). Dictionaries have the elements are "out of order", they are simply unordered. Examples: Example 3: >>> dict={'name':'ali', 'code':12016000,'dept':"engineering"} >>> dict['name'] 'ali' >>> dict.keys() ['dept', 'code', 'name'] >>> dict.values() ['Engineering', 12016000, 'ali'] >>> dict2={ } >>> dict2[ "one" ]=" this is one" #add a new element to dictionary >>> dict2 [2]= "this is two" >>> dict {2: 'this is two', 'one': ' this is one'} >>> del dict["one"] # delete element has a key one from dictionary >>> dict {2: 'this is two'} >>> dict.clear() # delete all elements >>> dict {}
Mathematical functions: 1. Build-in Functions The Python interpreter has a number of functions built into it that are always available: abs(x) The absolute value of x. cmp(x, y) -1 if x < y, 0 if x == y, or 1 if x > y max( seq ) return its largest item in sequence (String,List, Tuple ) min( seq) return its smallest item n sequence (String,List, Tuple ) sum (seq ) return the sum of a sequence (List, Tuple) of numbers len(seq) Return number of elements in sequence (String,List, Tuple ) Example 4: print "abs(-5) = ",abs(-5) print "list=[88,5,9], largest number in list is = ",max([88,5,9]) print "list=[88,5,9], smallest number in list is = ",min([88,5,9]) print "sum of a sequence of numbers [8,6,2,5] = ",sum([8,6,2,5]) print "compare two number :",cmp(8,5) Output: 2. Math module functions : The following functions are provided by this module, before use it we must invoke module using import keyword: ceil(x) Return the ceiling of x as a float, the smallest integer value greater than or equal to x. floor(x) Return the floor of x as a float, the largest integer value less than or equal to x. fabs(x) Return the absolute value of x as a float. sqrt(x) The square root of x for x > 0 log(x) The natural logarithm of x, for x> 0
log10(x) The base-10 logarithm of x for x> 0 Trigonometric Functions Return value of function in radians sin(x), cos(x), tan(x) radians(x) Converts angle x from degrees to radians. degrees(x) Converts angle x from radians to degrees. exp(x) The exponential of x: ex Constants: pi The mathematical constant π = 3.141592... e The mathematical constant e = 2.718281... How to use it: Example 5: import math # firstly we must import math module print "sin(90) = ",math.sin(math.pi/2) print "cos(180) = ",math.cos(math.pi) print "fabs(-5)=", math.fabs(-5) print "floor(5.9)=",math.floor(5.9) print "ceil(5.9)=",math.ceil(5.9) print "sqrt(49) =",math.sqrt(49) print "log10(1000) =",math.log10(1000) print "pi = ", math.pi print "degrees(math.pi/2) =",math.degrees(math.pi/2) print "e^2 = ",math.exp(2) print "log e ^2 = ",math.log(math.exp(2)) Output:
Exercises: 1) Write a Python program that compute the area of a circle given the radius entered by the user. Area = πr 2 2) Write a Python program to solve quadratic equations of the form ax 2 + bx + c = 0 Where the coefficients a, b, and c are real numbers taken from user. The two real number solutions are derived by the formula x = b ± b2 4ac 2a For this exercise, you may assume that a 0 and b 2 4ac 3) Write a program that define dictionary will save the following information entered by the user and then use it to print a payroll statement as the following example: Employee s name (e.g., ibraheem) Number of hours worked in a week (e.g., 13) Hourly pay rate (e.g., 6.75) Municipality tax rate (e.g., 20%) Country tax rate (e.g., 8%) Hint: dictionary will save information just about (Employee s name, Number of hours worked in a week, Hourly pay rate and Deductions). Output as the following image: