Studio: Functions

The reverse list method flips the order of the elements within an list. However, reverse does not affect the digits or characters within those elements.

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fun_list = ['hello', 'world', 123, 'orange']

fun_list.reverse()
print(fun_list)

['orange', 123, 'world', 'hello']

What if we wanted the reversed list to be ['egnaro', 321, 'dlrow', 'olleh']?

Let’s have some fun by creating a process that reverses BOTH the order of the entries in an list AND the order of characters within the individual elements.

Remember that a function should perform only one task. To follow this best practice, we will solve the list reversal by defining two functions - one that reverses the characters in a string (or the digits in a number) and one that flips the order of entries in the list.

To get started on the studio, open up data-analysis-projects/functions/studio/functions-studio.py.

Reverse Characters

1. In order to create this function, let’s review some string methods and list methods we learned about earlier. Using these built-in methods, we can create a function that will not only reverse the order of elements, but the characters contained within each element.

   1. Define the function as reverse_characters. Give it one parameter, which will be the string to reverse.
   2. Within your function, use the list function to split the string into a list of individual characters.
   3. reverse your new list.
   4. Use join to create the reversed string and return that string from the function.
   5. Create a variable of type string to test your new function. (See suggestions below)
   6. Use print(reverse_characters(my_variable_name)) to call the function and verify that it correctly reverses the characters in the string.
   7. Optional: Use method chaining to reduce the lines of code within the function.

Reverse Digits

2. The reverse_characters function works great on strings, but what if the argument passed to the function is a number type? Using print(reverse_characters(1234)) results in an error, since split only works on strings. When passed a number, we want the function to return a number with all the digits reversed (e.g. 1234 converts to 4321 and NOT the string "4321").

   1. Add an if statement to reverse_characters to check the type the parameter.
   2. If type is str, return the reversed string as before.
   3. If type is int or float, convert the parameter to a string, reverse the characters, then convert it back into a number.
   4. Return the reversed number.
   5. Be sure to print the result returned by the function to verify that your code works for both strings and numbers. Do this before moving on to the next exercise.

Complete Reversal

3. Now we are ready to finish our complete reversal process. Create a new function with one parameter, which is the list we want to change. The function should:

   1. Define and initialize an empty list.
   2. Loop through the old list.
   3. For each element in the old list, call reverse_characters to flip the characters or digits.
   4. Add the reversed string (or number) to the list defined in part ‘a’.
   5. Return the final, reversed list.
   6. Be sure to print the results from each test case in order to verify your code.

Submitting Your Work

Copy the URL to your GitHub repo and paste it in the submission box on the Canvas assignment page.