Names vs Objects¶

Core Distinction¶

Names are references to objects, not containers holding values:

x = [1, 2, 3]
# x is a name pointing to list object in heap

x ───► [1, 2, 3]   (heap object)
       │
       ├── id: 0x7f...
       ├── type: list
       └── value: [1, 2, 3]

The arrow (→) is a pointer/reference, not a copy.

x = [1, 2, 3]
y = x
z = x

# Multiple names, one object
print(x is y is z)  # True

x ─┬──► [1, 2, 3]
   │
y ─┤
   │
z ─┘

x = [1, 2, 3]

print(id(x))        # Identity
print(type(x))      # Type
print(x)            # Value

x = [1, 2, 3]
original_id = id(x)

x.append(4)
print(id(x) == original_id)  # True

x = [1, 2, 3]
y = x

print(id(x) == id(y))  # True

x = [1, 2, 3]
y = x

x = [4, 5, 6]

print(x is y)       # False