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class Something(object):
    pass # we need this because setting attributes on object instances is not allowed, e.g. object().x = 3 is not supported

def non_operation(a): # gets a reference to anything (a primary data type or an object)
    a = 3 # substitues a in this scope with 3
    
number, name, truthy, another_number, some_object, a_dict = 1, 'test', True, 1.1, Something(), {1:2} 
print(number, name, truthy, another_number, some_object, a_dict)
non_operation(number)
non_operation(name)
non_operation(truthy)
non_operation(another_number)
non_operation(some_object)
non_operation(a_dict)
print('nothing has changed:')
print(number, name, truthy, another_number, some_object, a_dict)

def cache_data(a, to_cache_number): # gets a 2 references
    b = a # creates a reference 'b' to the object also referenced by 'a'
    b.some_attribute = to_cache_number # substitues 'some_attribute' attribute on the object referenced by 'b' with the value 'to_cache_number'
    a = 3 # the reference 'a' not contains the primary data type int, value 3
    a += 10 # the reference 'a' not contains the primary data type int, value 13
    c = b 
    c.some_attribute += 1
    return b # returns the address of the value referenced by 'b'

cache_data(some_object, 3)

print('Will be the initial object ', some_object, 'since nobody can take that away from us and 4 since the value of the attribute was changed', some_object.some_attribute)

def sum(first_number=1, second_number=1):
    return first_number + second_number

print('sums')
print(sum(1, 10))
first_number, second_number = 1, 10 
print(sum(first_number, second_number)) # not needed, there is no relation

# but what is nicer is to be clear in what your are doing
# assuming sum was defined in another module
print(sum(first_number=1, second_number=10))
# is a lot clear to user than sum(1, 10)

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