Code Explanation:
🔹 1. Importing ChainMap
from collections import ChainMap
✅ Explanation
ChainMap is imported from Python's collections module.
It combines multiple dictionaries into one logical view.
It does not merge or copy dictionaries.
Instead, it simply keeps references to the original dictionaries.
Think of it like looking through multiple transparent sheets.
Sheet 1
x = 1
↓
Sheet 2
x = 5
y = 10
↓
ChainMap
Looks through Sheet 1 first,
then Sheet 2.
🔹 2. Creating the First Dictionary
a = {"x": 1}
✅ Explanation
A dictionary named a is created.
Memory:
a
↓
{
"x": 1
}
🔹 3. Creating the Second Dictionary
b = {"x": 5, "y": 10}
✅ Explanation
Another dictionary named b is created.
Memory:
b
↓
{
"x": 5,
"y": 10
}
Notice that both dictionaries contain the key:
"x"
but with different values.
🔹 4. Creating the ChainMap
c = ChainMap(a, b)
✅ Explanation
This line does not create a new dictionary.
Instead, Python creates a view over both dictionaries.
Current structure:
ChainMap
│
├── a
│ x = 1
│
└── b
x = 5
y = 10
Rule:
Search starts from
Dictionary 1
↓
If not found,
Dictionary 2
↓
Dictionary 3 ...
🔹 5. Updating Dictionary a
a["x"] = 100
✅ Explanation
The value of "x" inside dictionary a is changed.
Before:
a
↓
{
"x":1
}
After:
a
↓
{
"x":100
}
Important:
Since ChainMap stores a reference, it immediately sees this change.
Current memory:
a
↓
{
"x":100
}
b
↓
{
"x":5,
"y":10
}
🔹 6. Looking Up the Key
c["x"]
✅ Explanation
Python starts searching for "x".
Search order:
Dictionary a
↓
Found?
YES ✅
Value found:
100
Python does not continue searching in b.
Even though:
b
↓
x = 5
exists, it is ignored because the key was already found in the first dictionary.
🔹 7. Printing the Value
print(c["x"])
✅ Explanation
Python prints:
100
🎯 Final Output
100
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