Python Class Methods
Class Methods
Methods are functions that belong to a class. They define the behavior of objects created from the class.
Example
Create a method in a class:
class Person:
def __init__(self, name):
self.name = name
def greet(self):
print("Hello, my name is " + self.name)
p1 = Person("Emil")
p1.greet()
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Note: All methods must have self as the first parameter.
Methods with Parameters
Methods can accept parameters just like regular functions:
Example
Create a method with parameters:
class Calculator:
def add(self, a, b):
return a + b
def multiply(self, a, b):
return a * b
calc = Calculator()
print(calc.add(5, 3))
print(calc.multiply(4, 7))
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Methods Accessing Properties
Methods can access and modify object properties using self:
Example
A method that accesses object properties:
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def get_info(self):
return f"{self.name} is {self.age} years old"
p1 = Person("Tobias", 28)
print(p1.get_info())
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Methods Modifying Properties
Methods can modify the properties of an object:
Example
A method that changes a property value:
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def celebrate_birthday(self):
self.age += 1
print(f"Happy birthday! You are now {self.age}")
p1 = Person("Linus", 25)
p1.celebrate_birthday()
p1.celebrate_birthday()
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The __str__() Method
The __str__() method is a special method that controls what is returned when the object is printed:
Example
Without the __str__() method:
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
p1 = Person("Emil", 36)
print(p1)
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Example
With the __str__() method:
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def __str__(self):
return f"{self.name} ({self.age})"
p1 = Person("Tobias", 36)
print(p1)
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Multiple Methods
A class can have multiple methods that work together:
Example
Create multiple methods in a class:
class Playlist:
def __init__(self, name):
self.name = name
self.songs = []
def add_song(self, song):
self.songs.append(song)
print(f"Added: {song}")
def remove_song(self, song):
if song in self.songs:
self.songs.remove(song)
print(f"Removed: {song}")
def show_songs(self):
print(f"Playlist '{self.name}':")
for song in self.songs:
print(f"- {song}")
my_playlist = Playlist("Favorites")
my_playlist.add_song("Bohemian Rhapsody")
my_playlist.add_song("Stairway to Heaven")
my_playlist.show_songs()
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Delete Methods
You can delete methods from a class using the del keyword:
Example
Delete a method from a class:
class Person:
def __init__(self, name):
self.name = name
def greet(self):
print("Hello!")
p1 = Person("Emil")
del Person.greet
p1.greet() # This will cause an error
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