5StringFunction.md

Problem in F17: 14.3.4-14.3.5) Creating functions

Problem in S18: 25.4-25.5) Creating functions

Learning Objectives

• Define/Call function with a return value
• Define/Call function with an argument
• Determine if situation could benefit from a function
• Using operations on strings (*)

Problem: Write a function called hide_password that takes a password as a string and returns a "hidden" password string. The hidden password string should be the same length as the string give, but with all the characters replaced with a question mark.

For example, the function would convert "password" to "????????".

Call the function twice to test it (don't use your real password, that's a bad idea)

Step 0: Understanding the problem:

We need to write a function that takes a string and returns a string that is the same length but consists of only question marks. The first thing we'll need to do is figure out the length of the password string then we'll have to create a string of question marks the same length.

Step 1: Creating the function header:

We need to create a function called hide_password that takes a password string.

def hide_password(password): 

Step 2: Finding the length of the password:

To find the length of a string we can use the built in len function on the string. This function takes in a string and returns the length of that string. We can save that number in a variable called length

length = len(password)

Step 3: Creating a string of all question marks:

Now that we know how long to make the string of question marks, we need a way to create it. Luckily python makes this easy for us by allowing us to "multiply" strings by integers to duplicate them. For example, "VT" * 3 gives us the string "VTVTVT". With this we can create our string of question marks by multiplying a string with just a question mark by the length of the password, like this:

"?" * length

Step 4: Return the hidden password:

We can tell our function to return the string we created in Step 3 by adding the return statement before it:

return "?" * length

Now all the parts of our function can be put together:

def hide_password(password): 
	length = len(password)
	return "?" * length

Step 5: Calling the function:

Now we need to call our function and print the result twice.

print(hide_password("Password123"))
print(hide_password("12345"))

Side note, if either of these is your password, you should definitely change it.

Solution:

Putting everything together gives us the solution:

def hide_password(password): 
	length = len(password)
	return "?" * length

print(hide_password("Password123"))
print(hide_password("12345"))