CPSC120B
Fundamentals of Computer Science

Practice Session

• Sunday at 6PM

Reading Questions

Quiz

Function Scope

• Variables created inside a function only exist in a function

• They are local to the function

  def do_something():
      x = 1
  do_something()
  print(x)

• Variables created outside a function can be read inside the function
• They are global variables

• This is desirable when working with constant variable, otherwise discouraged

  x = 1
  def do_something():
      return x + 1
  print(do_something())

• Variables created outside a function can not be modified inside the function
• Instead it creates a new variable inside the function with the same name as the variable outside
• The local variable shadows the global variable

• This is desirable, it allows you to name variables inside of functions without having to worry about the function affecting code elsewhere

  x = 1
  def do_something():
      x = 2
  do_something()
  print(x)

• These same rules apply to parameters

• This is common when variables are used as the input to a function

  x = 1
  def do_something(x):
      x = 2
  do_something()
  print(x)

Functions Calling Functions

• Functions can call other functions

  def do_something(x):
      b = x + 1
      return b
  
  def do_something_else(x):
      a = do_something(x)
      c = a - 1
      return c
  
  print(do_something_else(2))

Lab