Download Lab 3 – Variable and Data Type II

Islamic University Of Gaza
Faculty of Engineering
Computer Engineering Department
Lab 3
Variable and Data Type II
Eng. Ibraheem Lubbad
October 7, 2016
Python Lists:
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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:
>>> items=["apple", "orange",100,25.5]
>>> items[0]
'apple'
>>> 3*items[:2]
['apple', 'orange', 'apple', 'orange', 'apple', 'orange']
>>> items[2]=items[2]+50
>>> items
['apple', 'orange', 150, 25.5]
>>> items[0:2]=[20,30] # replace some elements
>>> items
[20, 30, 150, 25.5]
>>> items[0:2]=[] # remove some elements
>>> items
[150, 25.5]
>>> items[2:2]=[200,400] # insert some elements
>>> items
[150, 25.5, 200, 400]
>>> del items[0] # delete element at index 0 from list
>>> items
[25.5, 200, 400]
>>> items.append("orange") # List.append(object) -- append object to end
>>> items
[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
Python Tuples:
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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.
For example:
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
Python Dictionary:
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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.
For example:
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)
cmp(x, y)
max( [ ] )
min( [ ] )
sum ( [ ] )
The absolute value of x.
-1 if x < y, 0 if x == y, or 1 if x > y
return its largest item
return its smallest item
return the sum of a sequence of numbers
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)
import math
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)
floor(x)
fabs(x)
sqrt(x)
log(x)
log10(x)
Trigonometric Functions
sin(x), cos(x), tan(x)…
Return the ceiling of x as a float, the smallest integer value greater
than or equal to x.
Return the floor of x as a float, the largest integer value less than or
equal to x.
Return the absolute value of x as a float.
The square root of x for x > 0
The natural logarithm of x, for x> 0
The base-10 logarithm of x for x> 0
Return value of function in radians
radians(x)
degrees(x)
exp(x)
Converts angle x from degrees to radians.
Converts angle x from radians to degrees.
The exponential of x: ex
Constants:
pi
e
The mathematical constant π = 3.141592...
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:
End
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
−𝑏 ± √𝑏 2 − 4𝑎𝑐
2𝑎
For this exercise, you may assume that a ≠ 0 and 𝑏 2 ≥ 4𝑎𝑐
𝑥=