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Python 2.7: Classes

Hands-On | 04 Dec 2016

In the example below of class syntax, the class in parantheses indicate the clsaas from which the new class inherits - in the current case it's object.

class Person(object):
    """Person class"""
    def __init__(self, name, phone, gender):
        self.name = name
        self.phone = phone
        self.gender = gender

    def description(self):
        print "Name: %s, phone: %s, gender %s" % (self.name, self.phone, self.gender)

    def is_male(self):
        if self.gender == 'male':
            return True
            return False

    def is_female(self):
        if self.gender == 'female':
            return True
            return False

person = Person("John", "+011111xxxx", "male");

# output: Name: John, phone: +011111xxxx, gender: male

# output: True
print person.is_male();

Class scope example

Notice how variable is_alive will be available to all the members of the Animal class:

class Animal(object):
    is_alive = True
    def __init__(self, name):
        self.name = name

zebra = Animal("Jeffrey")
giraffe = Animal("Bruce")
panda = Animal("Tach")

print zebra.name, zebra.is_alive
print giraffe.name, giraffe.is_alive
print panda.name, panda.is_alive

# output: Jeffrey True
# output: Bruce True
# output: Tach True


In the example below we have defined a class called Person which inherits from the object, and a class called Student, which inherits the Person.

class Person(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def description(self):
        print self.name, self.age

class Student(Person):
    def __init__(self, name, age, studentId):
        self.studentId = studentId
        return Person.__init__(self, name, age)

    def info(self):
        print "Student id number is: %s" % (self.studentId)

student = Student("Tom Jones", 26, 8928372)

# output: Tom Jones 26

# output: Student id number is: 8928372

Accessing parent class using super()

At any point in time you can access the parent / superclass of the current class by using super function:

class A(object):
    def test(self):
        print "This is the parent function"

class B(A):
    def test(self):
        print "This is the overridden function in the child"
    def parent_test(self):
        super(B, self).test()

# instantiating from the child class B
instance = B()

# accessing the test function
# output: This is the overridden function in the child

# accessing the parent function using super()
# output: This is the parent function
super(B, instance).test()

# accessing the parent function using parent_test, which is using super()
# output: This is the parent function

Another example:  using __repr__ and print method:

class Point3D(object):
    def __init__(self, x, y, z):
        self.x = x
        self.y = y
        self.z = z

    def __repr__(self):
        return "(%d, %d, %d)" % (self.x, self.y, self.z)

my_point = Point3D(1, 2, 3)

# will use __repr__ function of the class
# output: (1, 2, 3)
print my_point