ADVANCED LIST PROCESSING - IT……
ADVANCED LIST PROCESSING — ITERATOR AND GENERATOR
Advanced List Processing என்பது list அல்லது மற்ற iterable collections-ல் உள்ள elements-ஐ memory-efficient மற்றும் controlled way-ல் process செய்வது. இந்த topic-ல் இரண்டு முக்கிய concepts:
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31 programs 13 MCQs v4
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Definition
Advanced List Processing என்பது list அல்லது மற்ற iterable collections-ல் ……
Definition
1. Iterator 2. Generator…
Definition
Simple idea: List ↓ One item at a time process செய்ய ↓ Itera……
Simple Explanation
Suppose: numbers = [10, 20, 30, 40] Normal list already contains all values: 10 20 30 40 ஒரு for loop: for x ……
Flow
Iterable ↓ iter() ↓ Iterator ↓ next() ↓ One value ↓ next() ↓ Next value ↓ ... ↓ StopIteration Generat……
Definition
Iterator என்பது collection-ல் உள்ள elements-ஐ one by one ……
Explanation
Example
numbers = [10, 20, 30] இந்த list i……
Comparison
Iterable vs iterator
இந்த இரண்டு terms மிகவும் important. Iterable L……
Explanation
Example
numbers = [10, 20, 30] numbers is iterable.……
Explanation
it is iterator. Memory: Iterable ……
Explanation
Next value get: next(iterator……
Explanation
numbers = [10, 20, 30] List created. it = iter(numbers) Python list-க்கான iterator object create செய்கிறது……
Dry Run
numbers = [10, 20, 30]
Explanation
Stopiteration
Suppose: numbers = [10, 20] it = iter(numbers) print(next(it)) print(……
Important
StopIteration means: Iterator has no more values. It i……
Explanation
For loop and iterator
When writing: for x in [10, 20, 30]: print(x) Python conceptually does something similar to: it =……
Concept
Important concept
for loop = automatic iterator handling You ……
Explanation
Iterator with string
String is iterable. text = "ABC" it =……
Explanation
Iterator with tuple
data = (100, 200, 300) it = i……
Explanation
Iterator with dictionary
Dictionary iteration gives keys by default. student = { "name": "Arun", "ma……
Explanation
Iterator is stateful
Iterator remembers where it s……
Program
If later
It does not restart from 1. T……
Explanation
Iterator exhaustion
Once an iterator is fully consumed, it cannot automat……
Why second empty list? Iterat……
Explanation
New iterator required
To start again: it = iter(num……
Explanation
Iterator protocol
Python iterator protocol mainly requires: __iter__() ……
Explanation
Custom iterator
We can create our own iterator class. class Numbers: def __in……
Explanation
Custom iterator line explanation
self.current = 1 Starting value. def __iter__(self): return se……
Definition
Generator என்பது values-ஐ ஒரே நேரத்தில் எல்லாம் create/store செய்யாமல், தேவைப்படும் போது……
Simple Explanation
Normal function: def test(): return 10 Function returns value and ends. Generator function: def test(): yiel……
Syntax
Usage
Explanation
next(g) or:…
Important
Calling: g = numbers() does not execute the complete functi……
Dry Run
Generator dry run
Explanation
Yield
yield is the heart of generat……
Important
return → sends value → function ends yield……
Comparison
Return vs yield
Normal function: def test(): ……
Because function ends after f……
Output through loop: 10 20…
Explanation
Generator with for loop
def numbers(): yield 1 yield ……
for automatically calls gener……
Explanation
Generator using loop
Better real example: def generate_numbers(n): ……
Explanation
def generate_numbers(n): Generator function. for i ……
Important
Generator does not create full list: [……
Explanation
Generator for squares
Normal list processing: squares = []……
All values stored in list. Ge……
Values produced one-by-one.…
Comparison
List vs generator memory
Suppose: numbers = [x*x for x in range(1000000)] This creates and stores all one million values. Memory usage……
Explanation
Lazy evaluation
Lazy evaluation means: Do not……
Program
Example
Explanation
At this stage, all squares are not necessarily mat……
Explanation
Generator expression
Like list comprehension: [x*x for x in range(5)] Generator expres……
Program
Program generator expression
Comparison
List comprehension vs generator expression
List comprehension: result = ……
Output
Result
Program
Type
Program
Generator expression
Program
Type
Output similar to:…
Explanation
Generator exhaustion
Generators are iterators. Once consumed, they……
Because first list(g) consume……
Explanation
Generator state
Generator remembers local var……
Program
Example
Explanation
yield x x += 1 yield x x += 1……
x value is remembered between……
Explanation
Generator with condition
def even_numbers(n): for i in range(1, n ……
Explanation
Generator for list processing
Suppose list: numbers = [1, 2, 3, 4, 5] We need only squares of ev……
Processing: 1 → odd → ignore 2 → e……
Explanation
Chained processing
Generator expressions useful for data pipelines. numbers = range(1,……
Flow: 1..10 ↓ Filter even ↓ 2,4,6,8,1……
Comparison
Iterator vs generator
Iterator General object that produces one item at a time. Can be created using: iter() or……
Remember
Every generator is an iterator.……
Program
Example
Explanation
This is iterator. But it is n……
Explanation
Iterable iterator generator relation
Iterable | | iter() ↓ Iterator | | next() ↓ Values Generator: Generator ↓ ……
Important
Important difference list and iterator
List: numbers = [10, 20, 30] Can be traversed repeatedly: for x in numbers: print(x) for x in n……
Comparison
List vs generator
Explanation
Generator no indexing
List: numbers = [10, 20, 30] ……
Generator: g = (x for x in [1……
Why? Generator values are pro……
Explanation
Generator no len
This: g = (x for x in range(5)) print(len(g)) causes error. Generators do n……
Explanation
Next with default
next() can accept a default v……
Program
Example
This avoids visible StopItera……
Explanation
Why use iterators
Iterators useful when: Large collection process செய்ய One item at a time traverse செய்ய Memory usage reduce ……
Explanation
Why use generators
Generators useful when: Large number of values Infinit……
Explanation
Infinite generator
Generators can represent infi……
Program
Example
Program
Usage carefully
Generator doesn't need to create ……
Explanation
Fibonacci generator
Important advanced example: def fibonacci(n): a = 0……
Dry Run
Fibonacci dry run
Explanation
Memory efficiency
Consider: numbers = [x for x in range(10000000)] Python must maintain millions of integer references in a lis……
Comparison
Eager vs lazy
Eager Evaluation [x*x for x in range(5)] Immediately calculates: ……
Explanation
Example
next(g) one item at a time.…
Common Mistake
Common error 1
Calling next() directly on li……
Common Mistake
Error
TypeError Because list is iterable but no……
Common Mistake
Common error 2
Confusing return and yield. Wrong generator understanding: def numb……
Common Mistake
Common error 3
Trying to reuse exhausted generator……
Generator already consumed.…
Common Mistake
Common error 4
Trying indexing: g = (x for x……
Common Mistake
Error.
Generators are sequential, no……
Common Mistake
Common error 5
Thinking generator expression is tuple: x = (n*n for n……
Important
Iterator facts…
Important
1. Iterator gives one item at a time. 2. Created using iter(). 3. next() retriev……
Important
Generator facts…
Important
1. Generator is a special iterator. 2. Uses yield. 3. Produces values lazily. 4. M……
Memory Trick
For iterator: ITERATOR = ITER + NEXT iter() ↓ ……
Remember
return → END yield → PAUSE Most important……
MCQ
What does iter() do?…
TRB Point
Trb point 2
What does next() do? It retri……
TRB Point
Trb point 3
What happens after all iterat……
TRB Point
Trb point 4
Which keyword creates a gener……
MCQ
Which is a generator expressi……
TRB Point
Trb point 6
x = [1, 2, 3] y = iter(x) pri……
TRB Point
Trb point 7
What is output? g = (x for x ……
TRB Point
Trb point 8
What is the fundamental difference between return and yi……
MCQ
Every generator is:…
TRB Point
Trb point 10
Every iterator is a generator. False Correct: Ever……
Interview Point
Interview point 1
Why are generators memory efficient? Because generator does not store the……
Interview Point
Interview point 2
Difference between iterable a……
Explanation
Example
[1, 2, 3] Iterator: Can directl……
Interview Point
Interview point 3
Why can a list be reused but a generator often cannot? A list stores values. ……
Interview Point
Interview point 4
Is range() a generator? No. range() is an iterable se……
Program
Example
MCQ
Which function converts an it……
MCQ
Which function retrieves the ……
MCQ
When an iterator is exhausted……
MCQ
Which keyword is used in gene……
MCQ
What is the output? a = [10, ……
MCQ
Which uses lazy evaluation?…
MCQ
What is the type? x = (n*n fo……
MCQ
Which statement is correct?…
MCQ
yield does what?…
MCQ
Generator values are normally……
Practice
Practice 1
Predict: a = [5, 10, 15] it = i……
Practice
Practice 2
Predict: def test(): yield 10……
Practice
Practice 3
Predict: g = (x+1 for x in ra……
Practice
Practice 4
Predict: g = (x for x in range(3)……
Practice
Practice 5
Predict: def even(): for x in range(1, 7……
Summary
Iterator An iterator is an object that provides elements one at a time. numbers = [10, 20, 30] it = iter(numb……
Explanation
Short description
Iterator = Collection-ல் இருந்து values-ஐ one-by-one access செய்யும் object. Generator = Values-ஐ memory-ல் எ……
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