constructors and generators in python
Constructors provide initial values for an object's attributes and are defined using the keyword 'init'. They're automatically called when an object is instantiated. Generators use the keyword 'yield' and can create iterators for efficient looping. Generators return an iterable set of items one at a time. Instead of returning all the items at once, a generator yields them one at a time, allowing efficient memory usage and improved performance.
Introduction to Constructors and Generators
Constructors initialize new objects and set their initial state. Generators produce sequences of values iteratively without explicitly defining each value.
What are Constructors?
Constructors are a special method explicitly used for creating and initializing class objects of a class 🤔. When a new object is instantiated, the constructor method is automatically invoked in order to initialize the object's state properly 💻. Constructors serve several vital purposes. They can be used to set default values for an object's properties, enable objects to be initialized with different values at run-time 📅, and facilitate the inheritance of properties between classes 📚.
A constructor always has the same name as the class itself and does not have a return type 📝. Constructors can also accept parameters :123:, which can be used to pass in values for initializing the object's properties. For example, a "Student" class constructor might accept parameters for a student's name and grade level to create a new Student object with that information 📝. Objects without a constructor would have undefined property values by default, making them unusable.
Constructors ensure that objects are fully initialized with meaningful values as soon as they are created. They provide structure and consistency for objects in a class hierarchy and enable flexible object initialization that can support a variety of use cases 💡. Constructors are crucial for producing well-formed, properly instantiated objects in object-oriented programming languages 💻.
Different Types of Constructors
Python creates a default constructor automatically if no constructor is defined explicitly. This constructor doesn't take any arguments and doesn't do anything except create an object of the class.
Here is an example of a default constructor:
class MyClass: def __init__(self): pass obj = MyClass()
In the example above, MyClass has a default constructor, which doesn't do anything.
A parameterized constructor is a constructor that takes one or more arguments. This constructor is defined explicitly and can be used to initialize the class's instance variables.
Here is an example of a parameterized constructor:
class MyClass: def __init__(self, name, age): self.name = name self.age = age obj = MyClass("John", 30) print(obj.name) # Output: John print(obj.age) # Output: 30
In the example above, MyClass has a parameterized constructor which takes two arguments, name and age, and initializes the instance variables name and age with the values passed as arguments.
What are Generators?
Generators are instrumental in developing custom iterators and asynchronous programming. They can also generate data sequences by yielding values from the generator function. Generators permit a function to pause its execution and return a value, then resume where it left off when next invoked. This ability to stop and restart function execution enables generators to act as iterators. They can traverse through a sequence, yielding one element at a time, and keep their place in the sequence for the next call.
The pausing and resuming functionality of generators is enabled through the yield keyword. When a yield statement is reached, the generator yields the specified value and pauses its execution. On the next call, the function resumes after the yield statement. This allows a generator to produce a sequence of values over multiple calls.
Different Types of Generators
Advantages and disadvantages of Using Constructors and Generators
Examples of Constructors and Generators
# Constructors class Person: def __init__(self, name, age): self.name = name self.age = age # create objects of Person p1 = Person("John", 36) p2 = Person("Smith", 25)
The constructor takes two arguments, name, and age, and assigns them to instance variables. The instance variables can then be accessed and modified by other class methods.
# Generators def my_gen(): n = 1 print('This is printed first') # Generator function contains yield statements yield n n += 1 print('This is printed second') yield n n += 1 print('This is printed at last') yield n a = my_gen() next(a)
It contains yield statements that allow the function to return a sequence of values. The yield statement stops the function from executing further and returns the yielded value to the caller. When the function is called again, it resumes execution from the last yield statement.
Constructors are special methods used for initializing objects of a class. They set default values for object properties, enable objects to be initialized with different values at run-time, and facilitate inheritance. Generators are functions that create iterable sets of items one at a time and enable the creation of custom iterators for traversing collections of data. They can be leveraged to generate data sequences, pause and resume execution, and facilitate asynchronous programming.
Answer:c. An iterator that yields a sequence of values
Answer:d. A special type of method used to initialize an object
Answer:b. To produce a sequence of values
Answer:c. To initialize an object
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