What is Python List?

 What is Python List? 

 

DESCRIPTION

  • In Python, an inventory may be a mutable, means the values that it contain are often modified. 
  • An inventory may be a variable which will have a sequence of values assigned there to during a list, these values are referred to as elements or members. 
  • It’s collection which is ordered, changeable and allows duplicate members.

Defining an inventory

  • We define an inventory this way:
  • fruits = [“Mango”, “Apple”, “Orange”, “Banana”, “Grapes”]
  • In python lists are written with square brackets.
  • We define an inventory by enclosing everything to the proper of the equal check in square brackets.
  • Each element or member is separated by a comma and an area . 
  • The primary element during a list always has an index of 0, the second element an index of 1, and so on. 
  • An inventory element are often assigned any sort of value that we will assign to ordinary variables, for instance a string or variety . 
  • We will even mix the various sorts of values within the same list.
  • For example: collection = [“5”,”Abdulmomin”,”Where is”] 
  • During this example, collection [0] features a numerical value of 5, collection [1] features a value of “Abdulmomin”, and collection [2] features a value of “Where is”.

All the time remember that:

  • The primary element during a list always has an index of 0, not 1. this suggests that if the last element within the list has an index of 9, there are 10 items within the list. 
  • An equivalent naming rules we learned for ordinary variables apply.
  • Only letters, numbers, and underscores are legal. the primary character cannot be variety . No spaces. 
  • It is a good idea to form list names plural—fruits rather than fruit, for example—since an inventory usually contains multiple things.

Add items

  • We use the append () method to feature an item to the top of the list.
  • If we would like to feature “Straw berry”, within the end of the list fruits it’ll be as fruits = [“Mango”, “Apple”, “Orange”, “Banana”, “Grapes”, “Straw berry”]
  • The statement begins with the list name:fruits.append(“Straw berry”)
  • Next there is a dot: fruits.append(“Straw berry”)
  • Then the keyword append: fruits. append(“Straw berry”) 
  • Rather than appending a component to the top of an inventory , we will insert it into the list where we would like it.
  • We use the insert () method to feature an item at the required index.

Delete and take away elements

  • There are several methods to get rid of items from an inventory . 
  • We will delete any list element by specifying its index .
  • The remove () method removes the required item.
  • The pop () method removes the required index. we will pop a component off an inventory and append it or insert it to a different list.
  • The del keyword removes the required index. It also can delete the list completely.
  • Similarly, the clear () method empties the list.

Slicing

  • We will copy consecutive elements of an inventory to create another list. 
  • The primary number inside the brackets targets the primary element within the slice.

List Length

  • Use the len () function to work out what percentage items during a list.fruits = [“Mango”, “Apple”, “Orange”, “Banana”, “Grapes”, “Straw berry”]Result: 6
  • print(len(fruits))

Example: Print the amount of things within the list:

Concatenation of the list

  • In python, two or more lists are often joined or concatenate. 
  • One among the simplest ways are by using the + operator.List4 = [“x”, “y” , “z”]List6 = list4 + list5
  • print(list6)
  • List5 = [5, 6, 7]
  • Example: Join two list:
  • Result: [ “x”.”y”.”z”,5,6,7] 
  • We will join two lists by appending all the things from list4 into list5, one by one. 
  • We will also use the extend () method, which purpose is to feature elements from one list to a different list.

List Methods


Method                                                     Description

append()                  Adds a component at the top of the list

insert()                     Adds a component at the required position

extend()                  Add the weather of an inventory to the top of the present list

pop()                       Removes the element at the required position

remove()                 Removes the item with the required value

clear()                     Removes all the weather from the list

count()                    Returns No. of elements with the required value

copy()                      Returns a replica of the list

index()                     Returns index of 1st element with specified value

reverse()                  Reverses the order of the list

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