Nested branching¶

Nested branches are if statements in the branches of other if statements. Nested if statements can be found in one branch or the other, or in both branches of a larger if statement. This way of setting if statements can go to any depth, but it should be borne in mind that that way programs can become difficult to understand exactly and hard to maintain.

In the first example, we intentionally provide a program with three levels of nesting if statements, to help you imagine what a program with even more deeply nested and longer if statements might look like. In other examples and tasks, we will limit ourselves to one level of inserting if statements.

Examples and tasks¶

Example - guess who

There are eight children in the neighborhood who are often together. Their names are: Alice, Ben, Charlotte, Daniel, Emily, Frankie, Gabriella and Harry. Alice, Ben, Charlotte and Daniel go to the programming section, and Alice, Ben, Emily and Frankie to the sports section. The school cook wanted to praise one of the children for some deed, but did not know the name of that child.

Write a program that asks three questions, accepts the answers to those questions (the letter ‘y’ for yes, and every other answer for no) and prints out the name of the child in question. The questions the program asks are:

Is it a girl?
Does he or she go to the sports section?
Does he or she go to the programming section?

Note that programs with nested branches can be modified to use only consecutive conditions and form with elif, without inserting if statements in depth. In doing so, we use complex conditions, which we build using logical operations and, or and not.

Task - crossroads:

There is an intersection of A and B streets. The even house numbers in Street A are on the right and odd ones are on the left. On the even (right) side, the numbers up to the intersection are from 2 to 200, and after the intersection are those greater than 200. On the odd (left) side, the numbers up to the intersection are from 1 to 177, and after the intersection they are those from 179 onwards.

Write a program that loads one house number on street A and answers whether that number is before or after the intersection and which side of street A it is on. For example:

for number 128, print “on the right side, before the intersection”
for number 284 print “on the right side, after the intersection”
for number 177, enter “on the left side, before the intersection”
for number 219 write “on the left side, after the intersection”

Hint: After loading, you should first check if n is even, that is, if n % 2 == 0.

Task - studying:

John’s parents told John that if he received fours or fives in maths and English, he could go to an afternoon football tournament, otherwise he had to learn the subject or subjects from which he received grade(s) less than 4 (grades are from 1 to 5, 1 being the worst, 5 being the best).

Write a program that first loads John’s math grade and then English grade and prints a message for John. For example:

for grades 2, 3 print “learn math and English”
for grades 3, 4 print “learn math”
for grades 4, 2 print “learn English”
for grades 5, 4 print “go to the tournament”

Task - dressing up:

Ian is writing a program that reads the current temperature (in degrees Celsius) and the chance of rain (from 0 to 100) from the weather website, and based on that information, it writes a recommendation whether to bring a jacket (which has a hood) or an umbrella, or none of these two. Ian chose this rule:

when the temperature is below 21 Celsius, the advice should be: “wear the jacket”
when the temperature is 21 Celsius or higher and the chance of rain is over 50, the recommendation is: “bring an umbrella”
when the temperature is 21 Celsius or higher and the chance of rain is up to 50, the advice should be “you can go in a T-shirt”

The task for you is to write a program that loads the temperature first, then the chance of rain, and then prints a recommendation.