sample-programs/python/new_method.py at master · hansrajdas/sample-programs · GitHub

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#!/usr/bin/python

# Date: 2018-10-16
#
# Description:
# __new__() usage, it can be used to implement signletone pattern.


class A(object):
    _dict = dict()

    def __new__(cls):
        if 'key' in A._dict:
            print 'EXISTS'
            return A._dict['key']
        else:
            print 'NEW'
            return super(A, cls).__new__(cls)

    def __init__(self):
        print 'INIT'
        A._dict['key'] = self
        print ''


A()
A()
A()


# Output:
# ---------------------
# NEW
# INIT
#
# EXISTS
# INIT
#
# EXISTS
# INIT
#