Instance Variables
Object-specific data
Interview Relevant: Basic OOP
Instance Variables
Data unique to each object.
Code Examples
Instance variables for object state.
python
1class Counter:
2 def __init__(self):
3 self.count = 0 # Instance variable
4
5 def increment(self):
6 self.count += 1
7
8# Each object has its own count
9c1 = Counter()
10c2 = Counter()
11c1.increment()
12c1.increment()
13print(c1.count) # 2
14print(c2.count) # 0 (independent)
15
16# Add attributes dynamically
17c1.name = "Counter 1" # OK in Python!
18
19# Prevent dynamic attributes with __slots__
20class Strict:
21 __slots__ = ['x', 'y']
22 def __init__(self, x, y):
23 self.x = x
24 self.y = y
25
26s = Strict(1, 2)
27# s.z = 3 # AttributeError!