Structs in D Programming Language

Structs in Python#

In Python, we use classes to define similar data structures as structs in other languages. Here’s an example to illustrate the concept.

class Person:
    def __init__(self, name, age=0):
        self.name = name
        self.age = age

def new_person(name):
    p = Person(name)
    p.age = 42
    return p

def main():
    print(Person("Bob", 20))
    print(Person(name="Alice", age=30))
    print(Person(name="Fred"))
    print(Person(name="Ann", age=40))
    print(new_person("Jon"))

    s = Person(name="Sean", age=50)
    print(s.name)

    sp = s
    print(sp.age)

    sp.age = 51
    print(sp.age)

    dog = {"name": "Rex", "is_good": True}
    print(dog)

if __name__ == "__main__":
    main()

Explanation:#

• Class Definition: Python uses classes to define similar data structures as structs.
• Constructor: The __init__ method acts as the constructor.
• Creating Instances: Instances of the class are created by calling the class with the required arguments.
• Defining a Function: The new_person function creates a new Person instance and sets an age default.
• Accessing Object Properties: Properties of an instance are accessed using dot notation.
• Anonymous Structs: In Python, dictionaries serve the purpose of anonymous structs.

Running the Code:#

To run the program, save it to a file, for example, structs.py, and execute it with Python.

$ python structs.py
<__main__.Person object at 0x7f8301731c70>
<__main__.Person object at 0x7f8301731dc0>
<__main__.Person object at 0x7f8301731d30>
<__main__.Person object at 0x7f8301731df0>
<__main__.Person object at 0x7f8301731e50>
Sean
50
51
{'name': 'Rex', 'is_good': True}

Python does not display the content of objects directly, so to make it more readable, you could define a __str__ method in the Person class:

class Person:
    def __init__(self, name, age=0):
        self.name = name
        self.age = age

    def __str__(self):
        return f"Person(name={self.name}, age={self.age})"

With this change, the output will be more readable.

$ python structs.py
Person(name=Bob, age=20)
Person(name=Alice, age=30)
Person(name=Fred, age=0)
Person(name=Ann, age=40)
Person(name=Jon, age=42)
Sean
50
51
{'name': 'Rex', 'is_good': True}

Next example: Methods.