Input and Output Practice

These questions follow Data in Programs. Every program here talks to a person — which means a person can always type the unexpected.

Questions

Predict the output of each line — they are not the same.
```
print("Age:", 15)
print("Age:" + "15")
```

Predict the output when the user types Sam at the prompt.

name = input("Who is this? ")
print("Hi, " + name + "!")
print("Bye, " + name + ".")

Find the bug. Why does this crash, and what one change fixes it?

age = input("How old are you? ")
print("Next year you will be", age + 1)

In n = int(input("Number: ")), describe what happens when the user types 7 — and then what happens when they type seven.
Write a short program: ask for two numbers, print their sum. Test it with 3 and 4 — if it prints 34, you have found question 3.
Challenge. Ask for a word and a number, then print the word that many times on one line. cat and 3 should give catcatcat.

Answer 1

Age: 15 then Age:15. A comma in print inserts a space; + glues two strings with nothing added. Different tools.

Answer 2

Two lines: Hi, Sam! then Bye, Sam. — read once, reused twice.

Answer 3

age is a string — input() always returns text — so age + 1 adds text to a number: a TypeError. Wrap the input in int().

Answer 4

7 becomes the number 7 and all is well. seven defeats int() completely, and the program stops with a ValueError.

Answer 5

first = int(input("First number: "))
second = int(input("Second number: "))
print("Sum:", first + second)

Answer 6

word = input("Word: "), times = int(input("How many? ")), then print(word * times) — multiplying a string repeats it.

C1.3
identify various types of data and explain how they are used within programs
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C2.1
use variables, constants, expressions, and assignment statements to store and manipulate numbers and text in a program
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C2.2
write programs that use and generate data involving various sources and formats
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