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Notes about python

Object

# Base or Super class
class Person(object):
    def __init__(self, name):
        self.name = name
        
    def getName(self):
        return self.name
    
    def isEmployee(self):
        return False

# Employee subclass
class Employee(Person):
    def __init__(self, name, eid):

        ''' In Python 3.0+, "super().__init__(name)"
            also works''' 
        super(Employee, self).__init__(name)
        self.empID = eid
        
    def isEmployee(self):
        return True
        
    def getID(self):
        return self.empID

# Driver code
emp = Employee("Geek1", "E101") 
print(emp.getName(), emp.isEmployee(), emp.getID())

Lambda

Labda is an anonymous function also called also one function.

add = lambda a,b : x +b
print(add(4,8))
# Output will be: 12

def cube(y):
    return y*y*y;

g = lambda x: x*x*x
print(g(7))

print(cube(5))

List

Insert elements

List: dynamic sized arrays that contains duplicate values even of different data-types. append(): add a single element at the end of the list insert(): add element in specific index. list_name.insert(index, value_to_add) extend(): add multiple elements passing a list as argument list_number.extend([1,2,3])

Multidimensional lists

Multidimensional list:

myList = [['Davide', 'Pollicino'], [1,2,3]]
print(List[0][1]) # Will print out Davide

Remove elements from the list

# Raise an error if the element that does exists
list_name.remove(element_to_remove)

## Remove multiple element at the same time from index 0 to 4
for i in range(1, 5):
    list_name.remove(i)

# Remove last eleemnt 
list_name.pop()

Slicing a list

Slicing is one of the wayus used to print a list, using the ":" operator. Print list in reverse order [::-1] From begin to end [:]

Sliced_List = List[3:8]
print("\nSlicing elements in a range 3-8: ")
print(Sliced_List)

Get index of first occurency of an element

list_numbers = [1,2,3, 3,4]
# Raise an error because 5 does not exists
print(list_numbers.index(5))
# Will print 2
pritn(list_numbers.index(3))

sum : Ritorns the sum of the elements in the listprint(sum(my_list)) count : Ritorns the occurency of an element in the list print(my_list.count(element))

Set

Unrdered and unindexed collection. If you insert multiple times in the set it will not raise an error but once you print the content of the set you will see just isngle occurrencies of the elements

# Creat a set
my_set = {1,2,3,1}
# Convert list in Set
my_Set = set(list_name[1,3,4])

# Add a new element
my_Set.add(6)
# Add multiple elements 
my_Set.update([8,9])

Union of two list

def Union(lst1, lst2):
    final_list = list(set(lst1) | set(lst2))
    return final_list

Union of three or more list

def Union(lst1, lst2, lst3):
    final_list = list(set().union(lst1, lst2, lst3))
    return final_list

Intersaction of two list

With an intersaction operation we get all the element that are common between the two lists.

def get_intersaction(list1, list2):
    intersaction = [value for value in list1 if value in list2]
    return intersaction

def get_intersaction(list1, list2)
    return set(list1).intersaction(list2)

Stack

In python we can implement a stack just usign a list, with its built in functions append() and pop().

Queue

from collections import deque
my_queue = queue(["Davide", "Pino", "Alessio"])
print(my_queue)
my_queue.append("Antonino")
print(my_queue)
print(my_queue.pop())
print(my_queue)

Tuple

Immutable that datastruct (we cannot add / remove) any elemet.

# Create an empty list
my_tuple = ()