def my_function_name():
  #Function code


//Calling it
my_function_name()

Using Parameters

def my_function_name(my_variable1, my_variable2):
  #Function code

//Calling it
my_function_name(21, "abc")

my_function_name(my_variable1=21, my_variable2="abc")
my_function_name(my_variable2="abc", my_variable1=21)

Default values

def my_function_name(my_variable1, my_variable2="abc"):
  #Function code

//Calling it
my_function_name(21)
my_function_name(21, "def")

Return values

def my_function_name():
  return 21

//Calling it
return_value = my_function_name()

Multiple return values

def my_function_name():
  return 21, "abc", 55

//Calling it
return_value_1, return_value_2, return_value_3 = my_function_name()

Using a dictionary for multiple return values

#In the function:
    if something == True:
        return_values = {}
        return_values['Something1'] = "abc"
        return_values['Something2'] = "def"
        return_values['Something3'] = "ghi"
        return return_values

    return False

#Calling it
    return_value = my_function(camera_serial_number)
    if return_value != False:
        #### = return_value['Something2']

Calling a function before it is defined

Nope. You don’t do that in Python! All functions must be defined before they are used.