# 11.11. 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.

Example

 ```1 2 3 4``` ```fun_list = ['hello', 'world', 123, 'orange'] fun_list.reverse() print(fun_list) ```

Console Output

```['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.

## 11.11.1. Before You Start¶

Tip

We always encourage you to use local development at every opportunity. However, sometimes computers and software fail and we would rather you spend your studio time coding! If your computer is not cooperating with cloning your repo from Github, you can fork the starter code for the studio on Replit.

Code exercises 1 - 3 at repl.it

## 11.11.2. 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.

Tip

Use these sample strings for testing:

1. `'apple'`

2. `'LC101'`

3. `'Capitalized Letters'`

4. `'I love the smell of code in the morning.'`

## 11.11.3. Reverse Digits¶

1. 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 (TRY IT). 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.

Tip

Use these samples for testing:

1. `1234`

2. `'LC101'`

3. `8675309`

4. `'radar'`

## 11.11.4. Complete Reversal¶

1. 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.

Tip

Use this sample data for testing.

Input

Output

`['apple', 'potato', 'Capitalized Words']`

`['sdroW dezilatipaC', 'otatop', 'elppa']`

`[123, 8897, 42, 1138, 8675309]`

`[9035768, 8311, 24, 7988, 321]`

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

`['egnaro', 321, 'dlrow', 'olleh']`

## 11.11.5. Bonus Missions¶

1. Define a function with one parameter, which will be a string. The function must do the following:

1. Have a clear, descriptive name like `fun_phrase`.

2. Retrieve only the last character from strings with lengths of 3 or less.

3. Retrieve only the first 3 characters from strings with lengths larger than 3.

4. Use a template literal to return the phrase `We put the '___' in '___'.` Fill the first blank with the modified string, and fill the second blank with the original string.

1. Outside of the function, define the variable `str` and initialize it with a string (e.g. `'Functions rock!'`).

2. Call your function and print the returned phrase.

3. The area of a rectangle is equal to its length x width.

1. Define a function with the required parameters to calculate the area of a rectangle.

2. The function should return the area, NOT print it.

3. Call your area function by passing in two arguments - the length and width.

4. If only one argument is passed to the function, then the shape is a square. Modify your code to deal with this case.

5. Use a template literal to print, “The area is ____ cm^2.”

Tip

Use these test cases.

1. length = 2, width = 4 (area = 8)

2. length = 14, width = 7 (area = 98)

3. length = 20 (area = 400)