Of course! The phrase "if in range" in Python typically refers to using an if statement to check if a value is within a specific range of numbers. There are a few common ways to do this, each with its own advantages.

Let's break down the most important methods.

Method 1: The Simple if Statement with and (Most Common)

This is the most straightforward and readable method for checking if a number is between a minimum and a maximum value.

Syntax:

if minimum_value <= number <= maximum_value:
    # do something

How it works: This uses Python's chained comparison operators. The expression a <= b <= c is equivalent to a <= b and b <= c. It's clean, easy to read, and efficient.

Example:

score = 85
if 0 <= score <= 100:
    print("The score is a valid percentage.")
else:
    print("The score is out of the valid range.")
# --- Output ---
# The score is a valid percentage.

Example with a negative range:

temperature = -5
if -10 <= temperature <= 0:
    print("It's freezing cold!")
else:
    print("The temperature is above freezing.")
# --- Output ---
# It's freezing cold!

Method 2: Using the in Operator with range()

This method is useful when you want to check if a number is one of a specific set of discrete values, like checking for a day of the week or a list of valid options.

Syntax:

if number in range(start, stop):
    # do something

How it works: The range(start, stop) function generates a sequence of numbers from start up to (but not including) stop. The in operator then checks if your number exists within that sequence.

Key Point: The stop value is exclusive. range(1, 5) generates 1, 2, 3, 4.

Example: Let's check if a number is a single-digit number (i.e., between 0 and 9).

my_number = 7
# range(0, 10) generates numbers 0 through 9
if my_number in range(0, 10):
    print(f"{my_number} is a single-digit number.")
else:
    print(f"{my_number} is not a single-digit number.")
# --- Output ---
# 7 is a single-digit number.

Example with a different start value:

# Check if a number is in the 90s
grade = 95
if grade in range(90, 100):
    print("Grade is in the 90s (A).")
else:
    print("Grade is not in the 90s.")
# --- Output ---
# Grade is in the 90s (A).

Method 3: Using the in Operator with range() for Performance

This is a subtle but important performance tip. If you are checking if a number is within a very large range (e.g., 0 to 1,000,000), using if number in range(0, 1000000) can be inefficient.

The range() object doesn't create a list of all one million numbers in memory. Instead, it's a "lazy" object that generates numbers on the fly. However, the in operator still has to iterate through the sequence until it finds your number.

The faster way for large ranges is to use the simple comparison from Method 1.

Example (Performance Comparison):

big_number = 999_999
large_range = range(0, 1_000_000)
# Method 1: Simple Comparison (FAST)
# This is a direct mathematical check. It's O(1) complexity.
if 0 <= big_number <= 1_000_000:
    print("Method 1: Found using comparison.")
# Method 2: `in` with `range()` (SLOWER for large ranges)
# This has to iterate up to the number. It's O(n) complexity.
# For this example, it's almost instant, but for a range of 1 billion
# and a number near the end, the difference would be huge.
if big_number in large_range:
    print("Method 2: Found using `in range()`.")
# --- Output ---
# Method 1: Found using comparison.
# Method 2: Found using `in range()`.

Rule of Thumb:

• For checking if a number is between two values, use the simple comparison (if min <= num <= max).
• For checking if a number is in a set of discrete values (like 1, 2, 3, 4), use if num in range(...).

Summary Table

Real-World Example: Validating User Input

Let's combine these ideas to validate a user's age.

try:
    # Get input from the user
    user_age_str = input("Please enter your age: ")
    user_age = int(user_age_str)
    # Check 1: Is the age a reasonable positive number?
    if user_age >= 0:
        print("Age is a positive number.")
    else:
        print("Error: Age cannot be negative.")
    # Check 2: Is the age within a typical human lifespan?
    # Using the simple comparison method
    if 0 <= user_age <= 122: # 122 is the oldest recorded age
        print("Age is within a plausible human range.")
    else:
        print("Error: That age is not plausible.")
    # Check 3: Is the user a teenager? (13-19)
    # We can use the simple comparison here too, but `in range` also works well.
    if user_age in range(13, 20):
        print("You are a teenager.")
    else:
        print("You are not a teenager.")
except ValueError:
    # This block runs if the user enters text that is not a number
    print("Invalid input: Please enter a whole number for your age.")