Explanation:
🔹 Step 1: Create a List
[1]
The list contains only one element:
1
🔹 Step 2: Convert List into Iterator
x = iter([1])
iter() creates an iterator object.
Current iterator:
1
^
⚠️ Iterator remembers its current position.
🔹 Step 3: Execute First next(x)
next(x)
Python asks iterator:
Give me the next value
Iterator returns:
1
Now that value is consumed.
Iterator becomes:
END
^
No values left.
🔹 Step 4: Execute Second next(x)
next(x)
Again Python asks:
Give me the next value
But iterator has already reached:
END
There are no elements remaining.
🔹 Step 5: Python Raises Exception
Iterator cannot return any value.
So Python raises:
StopIteration
Program stops immediately.
⚡ Visual Trace
Initially
1
^
After First next(x)
Returned:
1
Iterator:
END
^
After Second next(x)
StopIteration
❌ Common Wrong Thinking
Many people think:
next(x)
will return:
None
when no values remain.
❌ Wrong.
Python actually raises an exception:
StopIteration
🎯 Final Result
Traceback (most recent call last):
...
StopIteration
.png)
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