How to define constructor for a class
What is a constructor
The constructor is a method which is called automatically right after an object has been created.
In Python we use __init__ as the constructor
name.
class FooBar:# w w w .j a va 2 s . c o m
def __init__(self):
self.somevar = 42
f = FooBar()
print f.somevar
The code above generates the following result.
The following code has a constructor with named parameter.
# from w w w . jav a 2 s.com
class FooBar:
def __init__(self, value=42):
self.somevar = value
f = FooBar('This is a constructor argument')
print f.somevar
The code above generates the following result.
Modifying Class Attributes
class counter:# from w w w .jav a 2 s . c om
count = 0
def __init__(self):
self.__class__.count += 1
counter
print counter.count
c = counter()
print c.count
print counter.count
d = counter()
print d.count
print c.count
print counter.count
Constructor with default parameter
class grocery:# ww w. ja va 2s . c om
def __init__(self, name, quantity=1):
self.name = name
self.quantity = quantity
items = {}
items['A'] = grocery('A')
items['B'] = grocery('B',2)
for item in items.keys():
print "Grocery : ", items[item].name,
print "\tQuantity: ", items[item].quantity
The code above generates the following result.
