# Invoking Functions

The first step to understand functions from a practical standpoint is using them. The fancy tech name we give to the action of "using" a function is "invoke a function". Python has many functions that we can just use out of the box. For example, print is a function (check the notes below) that lets you send characters to the console. Let's see a few different examples of invoking the print function:

print("Hello World")
print(42)

my_name = "Santiago"
print(my_name)

print("Santiago")

In this case, the function name is print. The only parameter that it receives is "something to print". So we invoke print passing as an argument that thing that we want to print in the screen.

Check the examples in the editor and complete the assignment: use the len and sum function to calculate length_of_hello_world and sum_of_first_10_numbers.

### Test Cases

test sum of first 10 numbers -

def test_sum_of_first_10_numbers():
assert sum_of_first_10_numbers == 55


test length of hello world -

def test_length_of_hello_world():
assert length_of_hello_world == 11


Solution 1

print("Hello World")

# The len function
print("Length of the string RMOTR:")
length_of_rmotr = len('RMOTR')
print(length_of_rmotr)

# The sum function
print("Sum of the first 5 numbers")
sum_of_first_5 = sum([1, 2, 3, 4, 5])
print(sum_of_first_5)

# Use the len function to replace -1 with the length of the string "Hello World"
# Use the sum function to replace -1 with the result of the sum of the first 10 numbers

print("Hello World") # The len function print("Length of the string RMOTR:") length_of_rmotr = len('RMOTR') print(length_of_rmotr) # The sum function print("Sum of the first 5 numbers") sum_of_first_5 = sum([1, 2, 3, 4, 5]) print(sum_of_first_5) # Your assignments: # Use the len function to replace -1 with the length of the string "Hello World" length_of_hello_world = -1 # Use the sum function to replace -1 with the result of the sum of the first 10 numbers # First 10 numbers being: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 (not including 0) sum_of_first_10_numbers = -1