Code Explanation:
🔹 1. Importing MappingProxyType
from types import MappingProxyType
✅ Explanation
MappingProxyType is imported from Python's built-in types module.
It creates a read-only (immutable) view of a dictionary.
It does not create a copy of the dictionary.
Any changes made to the original dictionary are immediately visible through the proxy.
Think of it as a glass window through which you can see the dictionary but cannot modify it.
types Module
│
▼
MappingProxyType
│
▼
Read-Only Dictionary View
Nothing executes yet.
🔹 2. Creating the Dictionary
data = {"x": 10}
✅ Explanation
A dictionary named data is created.
Current Memory
data
{
"x": 10
}
Visual Representation
data
│
└── x → 10
🔹 3. Creating the Read-Only View
view = MappingProxyType(data)
✅ Explanation
MappingProxyType() creates a read-only view of data.
Important:
It does not copy the dictionary.
Both data and view point to the same dictionary.
view simply prevents modifications through itself.
Current Memory
data
│
▼
{"x":10}
▲
│
view
Visual Representation
data
│
┌─────┴─────┐
│ │
▼ ▼
Original Read-Only View
Dictionary (MappingProxyType)
🔹 4. Modifying the Original Dictionary
data["y"] = 20
✅ Explanation
A new key-value pair is added to the original dictionary.
Current Memory
data
{
"x":10,
"y":20
}
Since view is connected to the same dictionary, it also sees the new key.
Visual Representation
Original Dictionary
x → 10
y → 20
▲
│
Read-Only View
🔹 5. Accessing Through the Proxy
print(view["y"])
✅ Explanation
Python looks for key "y" inside view.
Remember:
view points to the original dictionary.
Current Memory
view
↓
{
"x":10,
"y":20
}
The value of "y" is
20
So Python prints
20
🎯 Final Output
20
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