Python Find in List – How to Find the Index of an Item in a List (with example)
To Find the Index of an Item in a List, We can use the index() function, Which takes a single value as an argument and return the index (offset) of the value from the list
There are multiple ways to find an index of the list
- Using Index() function
- Using Loop
Quick Overview of the List
The list is a data structure, A well-organized way of storing data, We have seen multiple examples of declaring a variable like a=”hello” this is to store a single piece of data. Let’s say, You wanted to store multiple pieces of data which has some connection with each other
For example – Storing all the names of states in the US in an order Can be easily achieved by a list
states_of_america = ["Delaware", "Pennsylvania", "New Jersey", "Georgia", "Connecticut", "Massachusetts", "Maryland", "South Carolina", "New Hampshire", "Virginia", "New York", "North Carolina", "Rhode Island", "Vermont", "Kentucky", "Tennessee", "Ohio", "Louisiana", "Indiana", "Mississippi", "Illinois", "Alabama", "Maine", "Missouri", "Arkansas", "Michigan", "Florida", "Texas", "Iowa", "Wisconsin", "California", "Minnesota", "Oregon", "Kansas", "West Virginia", "Nevada", "Nebraska", "Colorado", "North Dakota", "South Dakota", "Montana", "Washington", "Idaho", "Wyoming", "Utah", "Oklahoma", "New Mexico", "Arizona", "Alaska", "Hawaii"]
In some cases, We might also want to have an order in your data server,
example – if you are storing all the people in a virtual Q, Then you want to keep a hold of the queue So that First come will be served First and last will be last served
This can be well achieved by the List (Same example)
How to access a specific value on the list
To access a specific value in a list, We need to know the offset, and can be used below
print(states_of_america[2])
states_of_america -> would be the variable name
2 -> Would be the index (offset)
So the offset will be counted from 0 -> 2 and in the above example the output would be
Output:
New Jersey
In the list, We can also use the negative index (Offset), Which will get the value in descending order
Example:
print(states_of_america[-2]) Alaska
To change a value in a list:
We can simply add the value below
states_of_america[2] = "New State" print(states_of_america[2])
Output:
New State
To add value to the end of the list
To add a single item or value to an end of a list, We can use the append() function
states_of_america.append("newly added state")
How to Find the Index of an Item in a List
Using Index() function
Using the Index() function is the best and most effective way in finding a value from a list. The index () function takes a single value as input and will give the index of the value from the list
Example:
letter=input("enter a letter in alphabet")
alphabet = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
position = alphabet.index(letter)
print("You letter is at " + str(position) + " position in an alphabet")
NOTE: Code designed to be compatible with online editor to test it
Output:
enter a letter in alphabet j You letter is at 9 position in an alphabet
Using LOOP
Just by iterating the values in the variable and finding the position of the matched value
Example:
letter=Input(“enter a letter in alphabet”)
alphabet = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']
for position in range(len(alphabet)):
if letter = alphabet[position]:
print("You letter is at " + str(position) + " position in an alphabet")
Output:
enter a letter in alphabet j You letter is at 9 position in an alphabet
Check here for Caesar Cipher example in python
Check here for more Python learning posts
Good Luck with your learning !!
