You will begin by creating the modules that hold the conversion functions. Start a new Python file and build each function to do the appropriate conversions.

Create a module named miles.

Create a function within this module named convertToMiles that accepts one value and returns the converted value when called.

Create a second module named kilometers.

Create a function within this module named convertToKilometers that accepts one value and returns the converted value when called.

Conversion formulas for your reference:

Metric Conversions $($Kilometers$-$to$-$miles$)$

Metric Conversions $($Miles$-$to$-$kilometers$)$

Hint: Modules are created as Python files with the same $.$py file extension as your main program file. Your modules must be within the same folder$/$directory as your program file in order to invoke functions from them.

Reference: Refer back to Learn to Program With Python $3$: A Step$-$by$-$Step Guide to Programming, $2$nd edition, Chapter $4$: Definition of a Function; and Programming in Python Chapter $7$: Python Modules $/7\mathrm{.}2$ Module Definition $/7\mathrm{.}3$ Creating a Module.

Next you will create your Python program to accept user input of a distance value and unit of length $($miles or kilometers$).$ You will start by including the import statements at the top of this program. You will import both the miles and kilometers modules you just created.

Reminder: These three Python files must exist within the same directory.

Reference: Refer to Programming in Python Chapter $7$: Python Modules $/7\mathrm{.}27\mathrm{.}57\mathrm{.}6$ Importing Modules.

Initialize variables. You should create two flag variables and initialize them to a value of true: one for when an invalid value is entered and one for when the user chooses to stop the processing $($i$.$e$.,$ validValue, processing$).$

Create a conditional loop that will continue the processing until the user chooses to exit.

Hint: Use the processing flag you just created in step $3$ as your test condition.

Reference: Refer back to Learn to Program With Python $3$: A Step$-$by$-$Step Guide to Programming, $2$nd edition, Chapter $6$: Loops $/$ The While Statement.

Accept a distance value and unit of length from the user and store these two values in variables. Use prompts such as:

Please enter a distance value:

What is the unit of length $($M $=$ miles, KM $=$ kilometers$)$:

Hint: Preface your input statement with float to ensure the value they enter is stored as a decimal number for use in the conversion formulas.

Reference: Refer back to your Unit $1$ readings in Learn to Program With Python $3$: A Step$-$by$-$Step Guide to Programming, $2$nd edition, Chapter $3$: Built$-$In Functions $/$ Getting Input From the User.

Incorporate a decision structure to check the unit of length entered by the user and call the appropriate conversion function from your user$-$defined modules.

If the user entered $$M$,$ call the convertToKilometers function passing in the user entered distance. Store the result of the function call in a new variable $($convertedDistance$).$

If the user entered $$KM$,$ call the convertToMiles function passing in the user entered distance. Store the result of the function call in a new variable $($convertedDistance$).$

Use an else statement for any other values and set the validValue flag to false to indicate an invalid value was entered.

Hint: Use the string function, upper, to convert the user input to uppercase and check for a value of M or KM only.

Reference: Refer back to Learn to Program With Python $3$: A Step$-$by$-$Step Guide to Programming, $2$nd edition, Chapter $5$: The if Statement $/$ Comparison Operators $/$ The elif Statement.

If the user entered a valid unit of length, display the distance they entered, the unit of measurement and the converted distance$/$unit$.$ Otherwise, display an error message. $($i$.$e$..$ Your distance of $26\mathrm{.}2$ miles is equivalent to $42\mathrm{.}1$ kilometers or You entered an invalid unit of length.$)$

Hint: Use an IF$/$ELSE decision structure here. Concatenate the results into one string.

Reference: Refer back to your Unit $1$ readings in Learn to Program With Python $3$: A Step$-$by$-$Step Guide to Programming, $2$nd edition, Chapter $2$: Print Statements; Chapter $3$: Built$-$In Functions $/$ Concatenation; Chapter $5$: The if Statement.

Add another prompt to ask the user if they would like to continue. $($i$.$e$.,$ Press X to quit or enter to continue processing.$)$

If the user entered a value to discontinue processing, set the processing flag to false to conclude the conditional looping and end the program.

Note: These small programming examples include very minimal data validation. Feel free to expand upon this and add additional layers of validation.

Example Output

Please enter a distance value: $26\mathrm{.}2$

What is the unit of length $($M $=$ miles, KM $=$ kilometers$)$ : m

Your distance of $26\mathrm{.}2$ miles is equivalent to $42\mathrm{.}16$ kilometers

Press X to quit or enter to continue processing.

Please enter a distance value: $5$

What is the unit of length $($M $=$ miles, KM $=$ kilometers$)$ : km

Your distance of $5.$