Understanding NaNs in Python

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” when we see them pop up unexpectedly. In this tutorial, we’ll dive into the world of NaNs (Not a Number) and learn how to handle them in Python’s math library.

First things first what exactly is a NaN? Well, it’s not really a number at all! It’s an IEEE 754 floating-point value that represents “not a number.” This can happen for various reasons, such as dividing by zero or taking the square root of a negative number.

Now, you might be wondering why would we even need something like this? Well, sometimes it’s useful to have a way to represent an invalid result without crashing our programs. For example, if we try to calculate the square root of a negative number using math.sqrt(), instead of getting an error message or causing our program to crash, we get a NaN back.

But here’s where things can get tricky how do we handle these ***** little values? In Python 3.5 and later versions, the math library has added some new functions specifically for dealing with NaNs: isfinite() and isnan(). Let’s take a look at each of them in turn.

isfinite(x)

This function returns True if x is neither an infinite nor a NaN value (including 0.0). If x is either inf or -inf, it will return False. This can be useful for checking whether a result is valid before using it further in our calculations. For example:

# Import the math module to access mathematical functions
import math

# Assign the square root of -9 to x, which will return a NaN value
x = math.sqrt(-9)

# Check if x is a finite value using the isfinite() function from the math module
if math.isfinite(x):
    # If x is finite, print a message indicating that the code should not run
    print("This should not run")
else:
    # If x is not finite, print a message indicating that the square root of a negative number is not finite
    print("The square root of a negative number is not finite.")

In this case, the if statement will never be executed because x is not finite (i.e., it’s either an infinite or NaN value).

isnan(x)

This function returns True if x is a NaN value and False otherwise. This can be useful for checking whether we have encountered a NaN in our calculations, which might indicate that something went wrong with our input data. For example:

# Import the math module to access mathematical functions
import math

# Assign a value to x that will result in an error
x = 1 / 0 # raises an error message

# Assign a value to y that will result in a NaN value
y = math.sqrt(-9) # returns NaN

# Check if x is a NaN value using the isnan() function
if math.isnan(x):
    print("We encountered a division by zero!") # Print a message if x is a NaN value

# Check if y is a NaN value using the isnan() function
elif math.isnan(y):
    print("The square root of a negative number is not defined.") # Print a message if y is a NaN value

In this case, the first if statement will be executed because x represents an invalid operation (division by zero), while the second if statement might or might not be executed depending on whether y contains a NaN value.

Remember, they may seem like ***** little values at first, but with the right tools and techniques, we can use them to our advantage and avoid crashing our programs when dealing with invalid input data.

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