6 Functions

Review¶

Wow, we've made a lot of progress here

• Variable types like integer, float, string, boolean, and list
• if statements using a boolean operator like ==, >, <
• for loops
• bringing together for loops with if statements

We also touched on

• The print() statement
• The use of # to make a free-form comment in our code (e.g. note to self)
• The importance of indentation/spacing in Python

The next concept is a Python function using def.¶

We will start with some examples.

In [6]:

# first we define a function to add to numbers
def add(a, b):
    result = a + b
    return result

# first we define a function to add to numbers def add(a, b): result = a + b return result

In [7]:

# now we will use our new function

print(add(1, 2))

result = add(3, 4)
print('result:', result)

# now we will use our new function print(add(1, 2)) result = add(3, 4) print('result:', result)

3
result: 7

In [8]:

# we can also pass our own variables to a function
firstNumber = 12
secondNumber = 20

result = add(firstNumber, secondNumber)

print('my result is:', result)

# we can also pass our own variables to a function firstNumber = 12 secondNumber = 20 result = add(firstNumber, secondNumber) print('my result is:', result)

my result is: 32

Important concept¶

Our function defined as

def add(a, b):
    return a + b

Does not expect a variable named a or b, it just expects a number for a and a number for b.

Recap on function¶

A function is a fundamental concept in mathematics.

It takes some inputs, performs a calculation, and return a result.

We have been using functions all along, print() is a function. It takes an input and prints it to the notebook.

Bringing it together¶

Lets use a function to test if our sensor is above a given threshold

In [9]:

# a function to test if a value is above a threshold
def isAboveThreshold(value, threshold):
    """Return True if value > threshold, otherwise False.
    """
    return value > threshold

# these are the values we have read from our sensor
sensorValues = [0, 3, 5, 7, 12, 15, 27, 35, 2, 2, 2, 100]

# we define a threshold where we want to report the value
threshold = 12

for sensorValue in sensorValues:
    if isAboveThreshold(sensorValue, threshold):
        print('WARNING: sensor value is above threshold', threshold, 'and has value', sensorValue)

# a function to test if a value is above a threshold def isAboveThreshold(value, threshold): """Return True if value > threshold, otherwise False. """ return value > threshold # these are the values we have read from our sensor sensorValues = [0, 3, 5, 7, 12, 15, 27, 35, 2, 2, 2, 100] # we define a threshold where we want to report the value threshold = 12 for sensorValue in sensorValues: if isAboveThreshold(sensorValue, threshold): print('WARNING: sensor value is above threshold', threshold, 'and has value', sensorValue)

WARNING: sensor value is above threshold 12 and has value 15
WARNING: sensor value is above threshold 12 and has value 27
WARNING: sensor value is above threshold 12 and has value 35
WARNING: sensor value is above threshold 12 and has value 100

Tutorial¶

• Write a funtion subtract that takes two variables. Your function will use - to subtract the given variables.
• Write a few lines of code to call your function with different values to subtract.

In [10]:

# enter your code here and click the run button to test it

# enter your code here and click the run button to test it