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Linear search is used to search for a target value in a list. We examine each of the elements in the list and compare them with the target value until matching the target.

If a match is found, the linear search function will return the index of the matching element. Otherwise, the function will raise a ValueError, a special error to indicate that the value was not found.

Here is the pseudocode for linear search as a function:

# For each element in the search_list
    # if element equal target value then
       # return its index
# if element is not found then 
    # raise a ValueError

Let’s convert the pseudocode into Python.

Instructions

1.

Declare a function called linear_search() in Python with two parameters: search_list, as its first parameter, and target_value, as its second parameter.

For now, in the body of your function, linear_search(), use the pass keyword.

pass is a placeholder in areas of your code where Python expects an expression.

2.

In the function linear_search():

  • Remove the pass keyword.
  • Create a for loop that iterates over the list using the range() and len() methods.
  • use the iterating variable to print each element in search_list

Uncomment the test code!

3.

Within the for loop after printing the element:

  • Use an if statement that checks whether the element matches target_value.
    • If so, return the index.
4.

If we complete the loop and there is not a match, use ValueError() to raise an exception.

Add a line outside the loop invoking raise ValueError() with "{target_value} not in list".

Interpolate target_value into the string, so if you’re searching for "biscuits" it reads: "biscuits not in list".

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