Sveip for å vise menyen

Understanding Iterators in Python

What Are Iterators?

Technically, in Python, an iterator is an object that implements the iterator protocol, which consists of the following methods:

__iter__(): returns the iterator object itself, making it compatible with loops like for;
__next__(): returns the next element in the sequence. When no elements remain, it raises a StopIteration exception to signal the end of traversal.

An iterator enables traversal of elements in an iterable (e.g., list or string) one at a time while keeping track of its position.


python

Note

An iterator is also an iterable because it implements the __iter__() method.

Not all iterables are iterators. For example, a list is iterable but not an iterator. When you pass it to the iter() function, you get an iterator that allows element-by-element traversal.

Building a Custom Iterator

This iterator generates a fixed number of random dice rolls and stops once all rolls are completed.


              123456789101112131415161718192021222324252627
            
import random

class FiniteDie:
    def __init__(self, num_rolls):
        """Initialize the iterator with a fixed number of rolls."""
        self.num_rolls = num_rolls
        self.current_roll = 0

    def __iter__(self):
        """Return the iterator object itself."""
        return self

    def __next__(self):
        """Generate the next dice roll or stop iteration."""
        if self.current_roll < self.num_rolls:
            self.current_roll += 1
            return random.randint(1, 6)
        raise StopIteration

# Using the FiniteDie iterator
num_rolls = 5
die_iterator = FiniteDie(num_rolls)

print(f"Rolling the die {num_rolls} times:")
for roll in die_iterator:
    print(f"Rolled: {roll}")

Iterator Exhaustion

Once an iterator is exhausted, it cannot be reused without recreating it. For example:


              12345678910
            
numbers = [1, 2, 3, 4]
iterator = iter(numbers)

# First iteration
for num in iterator:
    print(num)  # Output: 1, 2, 3, 4

# Second iteration
for num in iterator:
    print(num)  # Output: Nothing, the iterator is exhausted.

Iterators can only be traversed once. To iterate again, a new iterator needs to be created.

Oppgave

Swipe to start coding

Complete the missing parts of the code to implement a custom iterator class for simulating an infinite die roller. The iterator should lazily generate random rolls of a six-sided die and stop after 10 rolls.

The __iter__() method allows an object to be used as an iterator.
The __next__() method produces the next random die roll (a number between 1 and 6).
Create an instance of the InfiniteDie class, which represents the die roller.
Use a for loop with enumerate() to roll the die lazily. Stop after 10 rolls using an if condition and the break statement.

Løsning

Bytt til skrivebordet for virkelighetspraksisFortsett der du er med et av alternativene nedenfor

Alt var klart?

Takk for tilbakemeldingene dine!

Seksjon 6. Kapittel 2

Spør AI

Spør om hva du vil, eller prøv ett av de foreslåtte spørsmålene for å starte chatten vår

Understanding Iterators in Python

What Are Iterators?

Technically, in Python, an iterator is an object that implements the iterator protocol, which consists of the following methods:

__iter__(): returns the iterator object itself, making it compatible with loops like for;
__next__(): returns the next element in the sequence. When no elements remain, it raises a StopIteration exception to signal the end of traversal.

An iterator enables traversal of elements in an iterable (e.g., list or string) one at a time while keeping track of its position.


python

Note

An iterator is also an iterable because it implements the __iter__() method.

Not all iterables are iterators. For example, a list is iterable but not an iterator. When you pass it to the iter() function, you get an iterator that allows element-by-element traversal.

Building a Custom Iterator

This iterator generates a fixed number of random dice rolls and stops once all rolls are completed.


              123456789101112131415161718192021222324252627
            
import random

class FiniteDie:
    def __init__(self, num_rolls):
        """Initialize the iterator with a fixed number of rolls."""
        self.num_rolls = num_rolls
        self.current_roll = 0

    def __iter__(self):
        """Return the iterator object itself."""
        return self

    def __next__(self):
        """Generate the next dice roll or stop iteration."""
        if self.current_roll < self.num_rolls:
            self.current_roll += 1
            return random.randint(1, 6)
        raise StopIteration

# Using the FiniteDie iterator
num_rolls = 5
die_iterator = FiniteDie(num_rolls)

print(f"Rolling the die {num_rolls} times:")
for roll in die_iterator:
    print(f"Rolled: {roll}")

Iterator Exhaustion

Once an iterator is exhausted, it cannot be reused without recreating it. For example:


              12345678910
            
numbers = [1, 2, 3, 4]
iterator = iter(numbers)

# First iteration
for num in iterator:
    print(num)  # Output: 1, 2, 3, 4

# Second iteration
for num in iterator:
    print(num)  # Output: Nothing, the iterator is exhausted.

Iterators can only be traversed once. To iterate again, a new iterator needs to be created.

Oppgave

Swipe to start coding

The __iter__() method allows an object to be used as an iterator.
The __next__() method produces the next random die roll (a number between 1 and 6).
Create an instance of the InfiniteDie class, which represents the die roller.
Use a for loop with enumerate() to roll the die lazily. Stop after 10 rolls using an if condition and the break statement.

Løsning

Bytt til skrivebordet for virkelighetspraksisFortsett der du er med et av alternativene nedenfor

Alt var klart?

Takk for tilbakemeldingene dine!

Seksjon 6. Kapittel 2

Bytt til skrivebordet for virkelighetspraksisFortsett der du er med et av alternativene nedenfor