Python-3(List)

1. LIST:

1.1 introduction to list :

• A list is a collection which is ordered and changeable. In Python lists are written with square brackets.
• list is a data structure in Python that is a mutable, or changeable, ordered sequence of elements. Each element or value that is inside of a list is called an item. They enable you to keep data together that belongs together, condense your code, and perform the same methods and operations on multiple values at once.

     Examples :

1. Create a List:

   thislist = ["apple", "banana", "cherry"]
   print(thislist)
   

2. Print the single item of the list:

   thislist = ["apple", "banana", "cherry"]
   print(thislist[1])                                  #output  banana

3. Changing  the item of the list:

   thislist = ["apple", "banana", "cherry"]
   thislist[1] = "blackcurrant"                          #output  ['apple', 'blackcurrant', 'cherry']
   print(thislist)

1.2 Loop Through a List :

• we can loop through the list items by using a FOR loop

        Examples :

1. Print all items in the list, one by one:

   thislist = ["apple", "banana", "cherry"]
   for x in thislist:                                          #output   apple
   print(x)                                                              banana
                                                                         cherry
                                                                              

1.3 Check the Item Exists in the list :

• To determine if a specified item is present in a list use the IN keyword.

      Examples

1. Check if "apple" is present in the list:  

   thislist = ["apple", "banana", "cherry"]
   if "apple" in thislist:                                    #output  Yes, 'apple' is in the fruits list
   print("Yes, 'apple' is in the fruits list")

1.4 ADD and REMOVE the item in the list :

• To add an item to the end of the list, use the APPEND() method.
• REMOVE() or  POP() or  DEL  is used to remove the item in the list.

      Example  :

1. Add orange to the existing list :

   thislist = ["apple", "banana", "cherry"]
   thislist.append("orange")                          #output   ['apple', 'banana', 'cherry', 'orange']
   print(thislist)

2. removing the item using remove() method :

   thislist = ["apple", "banana", "cherry"]
   thislist.remove("banana")                          #output   ['apple', 'cherry']
   print(thislist)

3. removing the item using pop() method :

   thislist = ["apple", "banana", "cherry"]
   thislist.pop()                                             #output   ['apple', 'banana']
   print(thislist)

4. removing the item using del keyword :

   thislist = ["apple", "banana", "cherry"]
   del thislist[0]                                             #output  ['banana', 'cherry']
   print(thislist)

1.5 The list() Constructor :

• It is also possible to use the list() constructor to make a list.
• Using the list() constructor to make a List.

       Example :

1. constructor in list.

   thislist = list(("apple", "banana", "cherry")) # note the double round-brackets
   print(thislist)

1.6 List Methods :

• Following table shows the diffrent methods in list.