A linear search is used to check if a value is in an array. There are two ways of doing this:-

Check every value in the list, even if you find the value immediatly.

def linSearchV1(target,numbers):
    #Search for target in all of the numbers
    found=False
    for counter in range(len(numbers)):
        if numbers[counter]==target:
            found=True
    return found

Check until you find the value you are looking for, this is much more effient and can on average half the ammount of time taken for the program to run.

def linSearchV2(target,numbers):   
    #Search for the target numbers until it is found
    counter=0
    found=False
    while not found and counter!=len(numbers):
        if numbers[counter]==target:
            found=True
        else:
            counter=counter+1
    return found

The same algorithms can be used to find a string in an array of strings or a character in a string.