4 – More Branches

• Use multi-branch selection (if, elif, else statements) to control the flow of program execution
• Describe how iteration (while statements) controls the flow of program execution

• Multi-branch selection
• relational operators
• logical (or Boolean) expressions

• conditions
• iteration
• execution

Last lesson, you…

• Used selection (if statements) to control the flow of program execution
• Introduced elements of randomness into your programs

In this lesson, you will…

• Explore how selection can handle more than two possible branches
• Use iteration (while statements) to allow the flow of program execution to include loops

• How would you extend this program to give advice to the user on how to dress depending on the weather?
• Provide a rough outline of what your Python code would look like.
  • Give advice for when the weather is cloudy, rainy, or snowy.
  • In any other case, display a generic message.

Discuss in pairs and write your answer in the starter worksheet.

Download Starter Worksheet

• These versions of selection check one condition and select one out of two branches to follow.
• What if there are more than two cases in the problem?
• What if there are multiple branches ?

Think of the weather example:
“Give advice for when the weather is cloudy, rainy, or snowy.”

• Multi-branch selection (if, elif, else) checks successive conditions and selects one out of multiple branches to follow.

• You will need an if block with elif blocks: when there are more than two mutually exclusive paths for your program to follow.
• You can use multiple elif blocks.
• The else and its block are optional.
• You can nest anything inside the blocks of statements, even more if statements.

• Download this lesson’s worksheet to your Home Drive.
• Follow the instructions to complete the Silver/Gold task using the Activity 1 – People in Space – Silver/Gold in the repl.it window below.
• If you manage to complete the Silver/Gold task move onto the Platinum task below.

Silver/Gold Task

Platinum Task

• This program greets the user by name.

• What if…

• we wanted to repeat the process until a specific name is entered?
• Many of our programs have sections that could be repeated
• e.g. checking the weather for multiple locations, and a number guessing game with many guesses.

• When your programs repeat actions, checking for a terminating condition at the beginning of each new loop this is called a while loop.

• You will need a while statement: when your program needs to repeat actions while a condition is satisfied.

In this lesson, you…

• Explored how selection can handle more than two possible branches
• Used iteration (while statements) to allow the flow of program execution to include loops

Next lesson, you will…

• Use iteration (while statements) to allow the flow of program execution to include loops
• Use Boolean variables, operators, and expressions
• Use variables as counters and flags

• Mostly complete the Silver/Gold Task 1 – People in Space but your code does not meet all the requirements or there is an error and upload a screenshot of your code to bournetolearn.com.

• Complete the Silver/Gold Task 1 – People in Space and your code meets all the requirements and has no errors and upload a screenshot of your code to bournetolearn.com.

• Complete the Platinum Task – Temperature on the worksheet and upload a screenshot of your code to bournetolearn.com.