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Using Pi in Python (NumPy and Math)

Pi in Python Numpy Math Cover Image

In this tutorial, you’ll learn how to get and use the value of pi in Python. We’ll explore a number of different ways in which you can get and store the value of pi in Python. First, we’ll look at the math library, followed by the NumPy library. We’ll explore why you may want to choose one way over the other and close out with a fun alternative way of generating the value.

What is the Pi Constant?

The number pi, π, is a mathematical constant that’s approximately equal to 3.14159. It’s commonly used in Euclidian geometry to represent the ratio of a circle’s circumference to its diameter.

Pi itself is an irrational number, meaning that the value cannot be represented as a common fraction. However, the fraction 22/7 is often used to represent its value as an approximation. Similarly, the decimal representation of the value never ends and never moves into a permanently repeating pattern.

Pi in Python with Circumference and Diameter
Understanding how we can calculate Pi with the circumference and diameter of a circle

Now that you have a good understanding of the nature and uses of pi, let’s see how we can get this important mathematical constant in Python!

Get Pi in Python Using Math

In this section, you’ll learn how to use the math library to get the value of pi in Python. Because the math library is part of the standard Python library, you don’t need to install anything additional. Let’s see how we can import the value:

# Using math to Get the Value of Pi
import math

pi = math.pi
print(pi)

# Returns: 3.141592653589793

We can see that the constant pi is available simply by accessing the constant in the library.

If you’re only planning on using the constant from the library, it may make sense to import only that constant, rather than the whole library. This can be done as shown below:

# Only Importing Pi from Python math
from math import pi

pi_value = pi
print(pi_value)

# Returns: 3.141592653589793

This allows you to use the constant without needing to reference the library. In the next section, you’ll learn how to use the NumPy library to access the value of pi.

Get Pi in Python Using NumPy

Similar to the math library, the Python NumPy library provides the value of the pi constant. Since NumPy isn’t part of the standard Python library, you may need to install it. This can be done by using either pip or conda, as shown below:

$ pip install numpy
$ conda install numpy

Use either one of these installation methods, depending on your preferred package manager.

Once the library is installed, we can access the value of pi by using the constant in the library:

# Getting the Value of Pi in NumPy
import numpy as np

pi_value = np.pi
print(pi_value)

# Returns: 3.141592653589793

This method works similarly to how we would use the math library. Similarly, we can simply import the constant directly, if we only intend to use that value and nothing else from the library:

# Only Importing Pi from Python numpy
from numpy import pi

pi_value = pi
print(pi_value)

# Returns: 3.141592653589793

In the next section, we’ll explore when it’s better to use one method over the other.

Should You Use NumPy or Math to Get Pi in Python?

So far, you’ve learned two different ways to access the value of pi. At this point, you may be wondering which method is better to use. Before diving into that discussion, let’s first take a look if the value of the two constants is equal.

We can do this by using the == comparison operator:

# Comparing the two methods of getting pi in Python
import math
import numpy as np

math_pi = math.pi
numpy_pi = np.pi
print(math_pi == numpy_pi)

# Returns: True

Using the code above, we can see that the two values are the same. So, when would you use one over the other?

Because the math library is part of the standard Python library, using this approach means you’re not loading any additional dependencies. However, if you’re working with numerical calculations, there’s a good chance you’re using numpy already. In this case, it may be more straightforward simply to use the numpy approach.

So, in conclusion, the best method to use is the one that’s most useful to your circumstance. If you’re already using numpy in your program, you’re better off just using numpy’s pi constant. If you’re not using numpy, however, and want to keep your dependencies low, then you should use math.

Get Pi in Python Using Radians

Another fun way that you can get the value of pi in Python is to use the radians() function from the math library. When you pass in 180 as the value for the radian, the function returns the value of pi.

Let’s see what this looks like:

# Getting the Value of Pi with Radians
import math

pi = math.radians(180)
print(pi)

# Returns: 3.141592653589793

While this isn’t the most practical way to get the value of pi, it does work!

Conclusion

In this tutorial, you learned how to use Python to get the value of pi. You first learned about some of the basic properties of pi and why you may need a library to access its value. You then learned how to use both the math and numpy packages to get the value of pi. Finally, you learned how to use the radians() function to get the value of pi.

Additional Resources

To learn more about related topics, check out the articles below:

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