Check Natural Number in Python

What You’ll Learn

Under this tutorial’s rule, a natural number is an integer strictly greater than zero: n > 0. This page covers a reusable helper, listing 1..10, interactive input, a live checker, worked Python examples, edge cases, and complexity.

📝 Problem & Approach

Given an integer, decide whether it is natural under the rule n > 0, and optionally list natural numbers in a closed range.

# 42 -> natural
# 0  -> not natural (this page)
# -3 -> not natural

Inputs & Outputs

Minimal workflow

function is_natural(num):
    if num > 0:
        return true
    return false

Method comparison

🔮 Live Preview

Type an integer and check using the same rule as the code: n > 0.

Press “Check”.

Examples Gallery

Three complete Python programs — a yes/no helper, a 1..10 listing, and an interactive check with validation. Click View Output to reveal sample console results.

def is_natural(num: int) -> bool:
    return num > 0


def main() -> None:
    number = 42
    if is_natural(number):
        print(f"{number} is a natural number.")
    else:
        print(f"{number} is not a natural number.")


if __name__ == "__main__":
    main()

42 is a natural number.

def print_integers_in_range(start: int, end: int) -> None:
    print(f"Natural numbers in the range {start} to {end}:")
    for i in range(start, end + 1):
        print(i, end=" ")
    print()


def main() -> None:
    start = 1
    end = 10
    print_integers_in_range(start, end)


if __name__ == "__main__":
    main()

Natural numbers in the range 1 to 10:
1 2 3 4 5 6 7 8 9 10 

def is_natural(num: int) -> bool:
    return num > 0


def main() -> None:
    try:
        number = int(input("Enter an integer: ").strip())
    except ValueError:
        print("Could not read an integer.")
        return

    if is_natural(number):
        print(f"{number} is a natural number.")
    else:
        print(f"{number} is not a natural number.")


if __name__ == "__main__":
    main()

Enter an integer: 0
0 is not a natural number.

🔎 Worked Walkthrough — Sample Values

Apply num > 0 to a few integers.

Example 1 prints that 42 is a natural number.

⚖️ Facts Worth Knowing

Handy follow-ups interviewers sometimes ask.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

One comparison is constant time; listing grows with how many numbers you print.

💡 Best Practices