Read a value and check it

1. Input arrives as text

input reads one line from the terminal and returns a string without its ending newline. Type a value and press Enter. This example catches one expected conversion error; the full error-handling lesson explains try and except in more depth. Do not use eval to turn user text into a value.

In the output example, 4 is what you type at the prompt; the terminal normally echoes it. The program itself prints the prompt and the result.

raw = input("Pages: ")
try:
    pages = int(raw)
except ValueError:
    print("Enter a whole number.")
else:
    if 1 <= pages <= 50:
        print(f"Checking {pages} pages")
    else:
        print("Choose 1 to 50 pages.")

Pages: 4
Checking 4 pages

2. Conversion is not the whole rule

int accepts more than ASCII digits, including surrounding whitespace and a leading sign. That is acceptable for this practice prompt because the rule is simply a convertible whole number in a range. A strict file format would need a separate grammar. A valid integer such as 0 still fails our range rule.

3. Test more than the happy path

Run the program with 4, 0 and apple. Expect a success message, a range message and a conversion message respectively. Replacing the result with a silent default would hide a mistake. This interactive teaching script prints friendly messages and is not yet a CLI with failure exit codes.