More on Functions (class slides)

CSC 110 - More on Functions in Python

Function Comments

• Every function created is required to have a function comment, including main
• Function comments are a multi-line string (as opposed to using # for other comments)

Function Comments

'''
Xinchen Yu
CSC110
Class Demonstration
This program has two functions: one to calculate the area of a sphere,
the other to calculate the volume of a sphere.
The main() function is called to print to the standard output the
area and volume of a sphere of radius .75
'''
def sphere_area(radius):
  '''
  This function calculates the area of a sphere of given radius.
  Args:
    radius: integer representing the radius of the sphere
  Returns:
    The float representing the area of a sphere of the given radius
  '''
  area = 4 * 3.1415 * radius**2
  return round(area, 2)

def sphere_volume(radius):
  '''
  This function calculates the volume of a sphere of given radius.
  Args:
    radius: integer representing the radius of the sphere
  Returns:
    The float representing the volume of a sphere of the given radius
  '''
  volume = (1 / 3) * sphere_area(radius) * radius
  return round(volume, 2)

def main():
  '''
  This function prints the area and volume of a sphere of radius .75.
  Args:
    None
  Returns:
    None
  '''
  r = .75
  a = sphere_area(r)
  v = sphere_volume(r)
  print(a, v)
  
main()

7.07 1.77

Global vs. Local variables (scope)

• Every variable that is created has a particular scope
• The scope of a variable is the region in the code where the variable can be used or modified

Global vs. Local variables (scope)

• Local Variables have local scope – for example, a variable assigned inside a function can only be used or modified within that function
• Global Variables have global scope – for example, a variable delcared outside a function can be accessed or modified across multiple functions

Global vs. Local variables (scope)

• In the previous program we wrote (volume and area of sphere), r, v and a are local variables within the main() function.
• The variable radius and area are local within the sphere_area(radius) function scope.
• The variable radius and volume are local within sphere_volume(radius)

Global or Local?

a = 10               # What are the global and local variables?
b = 5                # Is the output of the two programs the same 
                     # or different?
def sum():
  return a + b

def main():
  print(sum())
  
main()

vs.

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

def main():
  print(sum(10, 5))
  
main()

Argument vs. Parameter

• Never set variables as global variables, pass values to functions when called
• When a function is defined, the variables you want to pass to the function are called parameter variables
• When the function is then called, the values you pass to the function are called arguments

Argument or Parameter?

# The parameters are a and b
def add(a, b):
    return a+b
  
# The arguments being passed through are 5 and 4
add(5, 4)

Write a function

Write a Python function called hypotenuse that takes two arguments: a and b representing the length of the two non-hypotenuse sides of a right triangle. The function should calculate the hypotenuse according to the Pythagorean theorem: \(c = \sqrt(a^2 + b^2)\). Return it rounded at two decimals.

Test cases: hypotenuse(3, 4) should return 5.0, hypotenuse(10, 10) should return 14.14

Name your file hypotenuse.py

Submit attendance

Submit your hypotenuse.py file with your solution to gradescope for attendance

Write a function

def sqrt(n):
  '''
  This function calculates the square root of a number
  Args:
    n: integer or float
  Returns:
    The square root of n
  '''
  return n**.5

def hypotenuse(a, b):
  '''
  This function calculates the hypotenuse of a right angle triangle.
  Args:
    a: number (integer or float) representing one of the non-hypotenuse sides
    b: number (integer or float) representing one of the non-hypotenuse sides
  Returns:
    Float representing the length of the hypotenuse given a and b
  ''' 
  h = sqrt(a**2 + b**2)
  return round(h, 2)

def main():
  '''
  This function calls the hypotenuse function to calculate and then
  print out the hypotenuse of a right angle triangle of sides 3 and 4
  and the hypotenuse of a right angle triange of sides 10 and 10
  '''
  result = hypotenuse(3, 4)
  print(result)
  
  result = hypotenuse(10, 10)
  print(result)
  
main()

5.0
14.14