Intermediate Object Oriented Python

Class¶

In [1]:

class Employee:
    def __init__(self, first,last, sal):
        self.first = first
        self.last = last
        self.sal = sal
    def fullname(self):
        return '{} {}'.format(self.first,self.last)

In [2]:

emp1 = Employee("arun","pra", 10)

In [3]:

emp2 = Employee("bal", "cm", 20)

In [4]:

emp1.fullname()

Out[4]:

'arun pra'

In [5]:

Employee.fullname(emp1)

Out[5]:

'arun pra'

Class variables¶

In [6]:

class Employee:
    def __init__(self, first,last, sal):
        self.first = first
        self.last = last
        self.sal = sal
    def fullname(self):
        return '{} {}'.format(self.first, self.last)
    def increment(self):
        self.sal = self.sal *1.05

In [7]:

emp1 = Employee("arun","pra", 10)
emp2 = Employee("bal", "cm", 20)

In [8]:

emp1.sal

Out[8]:

10

In [9]:

emp1.increment()
emp1.sal

Out[9]:

10.5

In [10]:

class Employee:
    incre_val = 1.05
    n_emp = 0
    def __init__(self, first,last, sal):
        self.first = first
        self.last = last
        self.sal = sal
        
        Employee.n_emp += 1
    def fullname(self):
        return '{} {}'.format(self.first, self.last)
    def increment(self):
        self.sal = self.sal *self.incre_val

In [11]:

print(Employee.n_emp)
emp1 = Employee("arun","pra", 10)
emp2 = Employee("bal", "cm", 20)
print(Employee.n_emp)

0
2

In [12]:

emp1.sal

Out[12]:

10

In [13]:

emp1.increment()
emp1.sal

Out[13]:

10.5

In [14]:

emp2.incre_val = 1.08

In [15]:

emp2.sal

Out[15]:

20

In [16]:

emp2.increment()
emp2.sal

Out[16]:

21.6

In [17]:

emp2.incre_val

Out[17]:

1.08

@classmethod, @staticmethod¶

In [18]:

class Employee:
    def __init__(self,first, last, sal):
        self.first, self.last, self.sal = first, last, sal
    def firstname(self):
        return '{} {}'.format(self.first, self.last)

In [19]:

e1 = Employee("arun","pra", 1000)

In [20]:

e1.sal

Out[20]:

1000

New usecase: create Employee from string "arun_prakash_1000"

In [21]:

emp_str = "prakash_pr_2000"
first,last,sal = emp_str.split("_")
e2 = Employee(first,last,sal)

In [22]:

e2.sal

Out[22]:

'2000'

Let's add the above functionality in the Employee class

In [23]:

class Employee:
    def __init__(self,first, last, sal):
        self.first, self.last, self.sal = first, last, sal
    def firstname(self):
        return '{} {}'.format(self.first, self.last)
    def ch(self,emp_str):
        self.first,self.last,self.sal = emp_str.split("_")
        

In [24]:

e1 = Employee.ch(emp_str)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-24-5a98d16ef119> in <module>()
----> 1 e1 = Employee.ch(emp_str)

TypeError: ch() missing 1 required positional argument: 'emp_str'

In [25]:

class Employee:
    def __init__(self,first, last, sal):
        self.first, self.last, self.sal = first, last, sal
    def firstname(self):
        return '{} {}'.format(self.first, self.last)
    @classmethod
    def from_string(cls,emp_str):
        first,last,sal = emp_str.split("_")
        return cls(first,last,sal)

In [26]:

emp_str = "prakash_pr_9000"
new_emp = Employee.from_string(emp_str)

In [27]:

new_emp.sal

Out[27]:

'9000'

In [28]:

import datetime
d = datetime.date(2016,10,7)

In [29]:

d

Out[29]:

datetime.date(2016, 10, 7)

staticmethod¶

In [30]:

class Employee:
    def __init__(self,first, last, sal):
        self.first, self.last, self.sal = first, last, sal
    def firstname(self):
        return '{} {}'.format(self.first, self.last)
    @classmethod
    def from_string(cls,emp_str):
        first,last,sal = emp_str.split("_")
        return cls(first,last,sal)
    @staticmethod
    def isworkday(day):
        if day.weekday() == 5 or day.weekday() == 6:
            return True
        else:
            return False

        

In [31]:

emp1 = Employee("arun","prak", 10000)

In [32]:

import datetime
d = datetime.date(2016,10,8)
print(d.weekday())
emp1.isworkday(d)

5

Out[32]:

True

Inheritance¶

In [33]:

class Employee:
    pay_r = 1.04
    def __init__(self, first, last, sal):
        self.first, self.last, self.sal = first, last, int(sal)
    def fullname(self):
        return '{} {}'.format(self.first, self.last)
    def pay_raise(self):
        self.sal = self.sal * self.pay_r
        
    @classmethod
    def cls_from_string(cls,emp_str):
        first,last,sal = emp_str.split("_")
        return cls(first,last,sal)
    @staticmethod
    def check():
        return 4
        

In [34]:

emp1 = Employee.cls_from_string("arun_prakash_10000")

In [35]:

emp1.fullname()

Out[35]:

'arun prakash'

In [36]:

print(emp1.sal)
emp1.pay_raise()
print(emp1.sal)

10000
10400.0

In [37]:

class Developer(Employee):
    pass
    

In [38]:

d1 = Developer("Arun", "Prak", 20000)

In [39]:

d1.fullname()

Out[39]:

'Arun Prak'

In [40]:

class Developer(Employee):
    def __init__(self,first,last,sal, lang):
        super().__init__(first,last,sal)
        self.lang = lang

In [41]:

d2 = Developer("arun", "praks", 20000, "python")

In [42]:

d2.lang, d2.sal

Out[42]:

('python', 20000)

In [43]:

d2.pay_raise()
d2.sal

Out[43]:

20800.0

In [44]:

class Developer(Employee):
    pay_r = 1.2
    def __init__(self,first,last,sal, lang):
        super().__init__(first,last,sal)
        self.lang = lang
d2 = Developer("arun", "praks", 20000, "python")

In [45]:

d2.sal

Out[45]:

20000

In [46]:

d2.pay_raise()

In [47]:

d2.sal

Out[47]:

24000.0

In [48]:

isinstance(d2,Employee)

Out[48]:

True

In [49]:

isinstance(d2, Developer)

Out[49]:

True

In [50]:

issubclass(Developer, Employee)

Out[50]:

True

Dunder methods¶

In [51]:

class Employee:
    def __init__(self, first, last, sal):
        self.first,self.last,self.sal = first,last,sal
    def fullname(self):
        return '{} {}'.format(self.first,self.last)
    

In [52]:

e1 = Employee("Arun","Prakash",10000)

In [53]:

e1.fullname()

Out[53]:

'Arun Prakash'

In [54]:

print(e1)

<__main__.Employee object at 0x11072df60>

In [55]:

str(e1)

Out[55]:

'<__main__.Employee object at 0x11072df60>'

In [56]:

class Employee:
    def __init__(self, first, last, sal):
        self.first,self.last,self.sal = first,last,sal
    def fullname(self):
        return '{} {}'.format(self.first,self.last)
    def __repr__(self):
        return 'Employee( {}, {} ,{})'.format(self.first,self.last,self.sal)
    def __str__(self):
        return self.fullname()
    def __add__(self,e):
        return self.sal + e.sal
    def __len__(self):
        return len(self.fullname())

In [57]:

e1 = Employee("Arun","Prakash",10000)
print(e1)

Arun Prakash

In [58]:

len(e1)

Out[58]:

12

In [59]:

e2 = Employee("ar","pr", 20000)

In [60]:

e1+e2

Out[60]:

30000

@property, setter, getter, deleter¶

In [61]:

class Employee:
    def __init__(self, first,last,sal):
        self.first, self.last, self.sal = first,last,sal
        self.email = self.first+"."+self.last +"@email.com"
    def fullname(self):
        return '{} {}'.format(self.first, self.last)
    

In [62]:

e1 = Employee("arun","prak", 10000)

In [63]:

e1.fullname()

Out[63]:

'arun prak'

In [64]:

e1.email

Out[64]:

'arun.prak@email.com'

In [65]:

print(e1.first)

arun

In [66]:

e1.first = "Arun"

In [67]:

print(e1.first)
print(e1.email)
print(e1.last)

Arun
arun.prak@email.com
prak

In [68]:

class Employee:
    def __init__(self, first,last,sal):
        self.first, self.last, self.sal = first,last,sal
    @property
    def email(self):
        return self.first+"."+self.last +"@email.com"
    def fullname(self):
        return '{} {}'.format(self.first, self.last)
    

In [69]:

e1 = Employee("arun","prak", 10000)
print(e1.first)
print(e1.email)
print(e1.last)

arun
arun.prak@email.com
prak

In [70]:

e1.first = "Arun"

In [71]:

print(e1.first)
print(e1.email)
print(e1.last)

Arun
Arun.prak@email.com
prak

In [72]:

class Employee:
    def __init__(self, first,last,sal):
        self.first, self.last, self.sal = first,last,sal
    @property
    def email(self):
        return self.first+"."+self.last +"@email.com"
    @property
    def fullname(self):
        return '{} {}'.format(self.first, self.last)
    

In [73]:

e1 = Employee("arun","prak", 10000)

In [74]:

print(e1.first)
print(e1.fullname)
print(e1.last)

arun
arun prak
prak

In [75]:

e1.fullname = "Arun Prakash"

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-75-0582b7cda382> in <module>()
----> 1 e1.fullname = "Arun Prakash"

AttributeError: can't set attribute

In [81]:

class Employee:
    def __init__(self, first,last,sal):
        self.first, self.last, self.sal = first,last,sal
    @property
    def email(self):
        return self.first+"."+self.last +"@email.com"
    @property
    def fullname(self):
        return '{} {}'.format(self.first, self.last)
    @fullname.setter
    def fullname(self,name):
        first,last = name.split(" ")
        self.first = first
        self.last = last
    @fullname.deleter
    def fullname(self):
        print("Deleting the name")
        self.first = None
        self.last = None
    

In [82]:

e1 = Employee("arun","prak", 10000)

In [83]:

print(e1.first)
print(e1.fullname)
print(e1.last)

arun
arun prak
prak

In [84]:

e1.fullname = "Arun Prakash"

In [85]:

print(e1.first)
print(e1.fullname)
print(e1.last)

Arun
Arun Prakash
Prakash

In [86]:

del e1.fullname

Deleting the name

In [87]:

print(e1.first)
print(e1.fullname)
print(e1.last)

None
None None
None