Some tools aren't part of core Python — you bring them in with import. A collection of tools you import like this is called a module.
Today's Module: math
Constants and functions for more advanced math than +, -, *, and / can do alone.
import math
math.pi
A constant — no parentheses, because you're not calling a function, just reading a stored value.
radius =float(input("Enter radius: "))
circumference =2* math.pi* radius
print(f"Circumference: {circumference}")
math.pi
Terminal window
Enter radius: 42 [Enter]
Circumference: 263.89378290154264
That Number Is Ugly. Fix It With round()
round() is built in — no math. needed. One argument rounds to a whole number; a second argument rounds to that many decimal places.
print(round(263.8938))
print(round(263.8938,2))
That Number Is Ugly. Fix It With round()
Terminal window
264
263.89
Wait — Haven't We Done Exponents Already?
Activity 1.4 taught ** for exponents. math.pow() does the exact same job.
side =2
print(side **3)
print(math.pow(side,3))
One Real Difference
Terminal window
8
8.0
math.pow() always returns a float, even when the answer is a whole number. ** doesn't. In your own code, ** is still the more common choice — but you'll see math.pow() in other people's code, so it's worth recognizing.
math.sqrt()
Square roots — no exponent trick required.
print(math.sqrt(45))
math.sqrt()
Terminal window
6.708203932499369
Today's Objectives
Importing a module for the first time
Using the math.pi constant
Rounding with round()
Comparing math.pow() to **
Calculating square roots with math.sqrt()
Key Terms
Module
A collection of tools not built directly into Python — you bring it in with import.
Constant
A named value, like math.pi, that doesn't change — read directly, not called with ().
round()
Built-in function that rounds a number, optionally to a specific number of decimal places.
math.pow()
Raises a number to a power, same job as **, but always returns a float.
math.sqrt()
Returns the square root of a non-negative number.
'F' → Fullscreen
Build
Create a new Python program named 1-9-math-functions.
Task 1: Circumference Calculator
Import the math module.
Ask the user for a radius, then calculate and print the circumference using math.pi.
Print the circumference again, rounded to 2 decimal places with round().
Math Functions
1
import math
2
3
radius =float(input("Enter radius: "))
4
circumference =2* math.pi* radius
5
6
print(f"Circumference: {circumference}")
7
print(f"Rounded: {round(circumference,2)}")
Task 2: ** vs. math.pow()
Ask for a side length and an exponent.
Print the result using **, then print the result using math.pow(), each labeled.
Math Functions
1
import math
2
3
radius =float(input("Enter radius: "))
4
circumference =2* math.pi* radius
5
6
print(f"Circumference: {circumference}")
7
print(f"Rounded: {round(circumference,2)}")
8
9
side =float(input("Enter a side length: "))
10
exponent =int(input("Enter an exponent: "))
11
12
print(f"{side} ** {exponent} is {side ** exponent}")
13
print(f"math.pow({side}, {exponent}) is {math.pow(side, exponent)}")
Task 3: Square Roots
Ask for a positive number and print its square root using math.sqrt().
Math Functions
1
import math
2
3
radius =float(input("Enter radius: "))
4
circumference =2* math.pi* radius
5
6
print(f"Circumference: {circumference}")
7
print(f"Rounded: {round(circumference,2)}")
8
9
side =float(input("Enter a side length: "))
10
exponent =int(input("Enter an exponent: "))
11
12
print(f"{side} ** {exponent} is {side ** exponent}")
13
print(f"math.pow({side}, {exponent}) is {math.pow(side, exponent)}")
14
15
number =float(input("Enter a positive number: "))
16
print(f"Square root of {number} is {math.sqrt(number)}")
Challenge (Optional): Ceiling and Floor
Look up math.ceil() and math.floor() in the Python docs.
Print a decimal number three ways: rounded, ceiling, and floor, and compare all three.
Checkpoint
Verify your program works correctly.
Example Output
Enter radius: 42 [Enter]
Circumference: 263.89378290154264
Rounded: 263.89
Enter a side length: 2 [Enter]
Enter an exponent: 3 [Enter]
2.0 ** 3 is 8.0
math.pow(2.0, 3) is 8.0
Enter a positive number: 45 [Enter]
Square root of 45.0 is 6.708203932499369
Reflection
Answer the following questions before submitting your work.
What is a module, and why does math need to be imported when round() doesn't?
What's the one real difference between ** and math.pow(), since they do the same job?
Why does math.pi get used without parentheses, while math.sqrt() needs them?
Submit
Submit the required files to the appropriate dropbox.
