The examples above are classes and objects in their simplest form, and are not really useful in real life applications. Show
To understand the meaning of classes we have to understand the built-in __init__() function. All classes have a function called __init__(), which is always executed when the class is being initiated. Use the __init__() function to assign values to object properties, or other operations that are necessary to do when the object is being created: ExampleCreate a class named Person, use the __init__() function to assign values for name and age: class Person: p1 = Person("John", 36) print(p1.name) Note: The The __str__() FunctionThe __str__() function controls what should be returned when the class object is represented as a string. If the __str__() function is not set, the string representation of the object is returned: ExampleThe string representation of an object WITHOUT the __str__() function: class Person: p1 = Person("John", 36) print(p1) ExampleThe string representation of an object WITH the __str__() function: class Person: def __str__(self): p1 = Person("John", 36) print(p1) Try it Yourself »Object MethodsObjects can also contain methods. Methods in objects are functions that belong to the object. Let us create a method in the Person class: ExampleInsert a function that prints a greeting, and execute it on the p1 object: class Person: def myfunc(self): p1 = Person("John", 36) Note: The The self ParameterThe It does not have to be named ExampleUse the words mysillyobject and abc instead of self: class Person: def myfunc(abc): p1 = Person("John", 36) Modify Object PropertiesYou can modify properties on objects like this: Delete Object PropertiesYou can delete properties on objects by using the Delete ObjectsYou can delete objects by using the The pass Statement
Lists are one of 4 built-in data types in Python used to store collections of data, the other 3 are Tuple, Set, and Dictionary, all with different qualities and usage. Lists are created using square brackets: ExampleCreate a List: thislist = ["apple", "banana", "cherry"] List ItemsList items are ordered, changeable, and allow duplicate values. List items are indexed, the first item has index OrderedWhen we say that lists are ordered, it means that the items have a defined order, and that order will not change. If you add new items to a list, the new items will be placed at the end of the list. Note: There are some list methods that will change the order, but in general: the order of the items will not change. ChangeableThe list is changeable, meaning that we can change, add, and remove items in a list after it has been created. Allow DuplicatesSince lists are indexed, lists can have items with the same value: ExampleLists allow duplicate values: thislist = ["apple", "banana", "cherry", "apple", "cherry"] List LengthTo determine how many items a list has, use the ExamplePrint the number of items in the list: thislist = ["apple", "banana", "cherry"] List Items - Data TypesList items can be of any data type: ExampleString, int and boolean data types: list1 = ["apple", "banana", "cherry"] A list can contain different data types: ExampleA list with strings, integers and boolean values: list1 = ["abc", 34, True, 40, "male"] Try it Yourself »type()From Python's perspective, lists are defined as objects with the data type 'list': ExampleWhat is the data type of a list? mylist = ["apple", "banana", "cherry"] The list() ConstructorIt is also possible to use the list() constructor when creating a new list. ExampleUsing the thislist = list(("apple", "banana", "cherry")) # note the double round-brackets Python Collections (Arrays)There are four collection data types in the Python programming language:
*Set items are unchangeable, but you can remove and/or add items whenever you like. **As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered. When choosing a collection type, it is useful to understand the properties of that type. Choosing the right type for a particular data set could mean retention of meaning, and, it could mean an increase in efficiency or security. What is class list in Python?We can create a list of objects in Python by appending class instances to the list. By this, every index in the list can point to instance attributes and methods of the class and can access them. If you observe it closely, a list of objects behaves like an array of structures in C.
What is __ contains __ in Python?Python string __contains__() is an instance method and returns boolean value True or False depending on whether the string object contains the specified string object or not. Note that the Python string contains() method is case sensitive.
Can a class be a list?To be more concrete, list is a class object (remember that “class” and “type” are synonymous) - it is the same sort of object that is produced when a class definition is executed.
Why list () is used in Python?Lists are used to store multiple items in a single variable. Lists are one of 4 built-in data types in Python used to store collections of data, the other 3 are Tuple, Set, and Dictionary, all with different qualities and usage.
|