README.md

Background Context

Now that we understand that everything is an object and have a little bit of knowledge, let’s pause and look a little bit closer at how Python works with different types of objects.

BTW, have you ever modified a variable without knowing it or wanting to? I mean:

>>> a = 1
>>> b = a
>>> a = 2
>>> b
1
>>>

OK. But what about this?

>>> l = [1, 2, 3]
>>> m = l
>>> l[0] = 'x'
>>> m
['x', 2, 3]
>>>

This project is a little bit different than the usual projects. The first part is only questions about Python’s specificity like “What would be the result of…”. You should read all documentation first (as usual :)), then take the time to *think and brainstorm with your peers about what you think and why. Try to do this without coding anything for a few hours.

Trying examples in the Python interpreter will give you most of the answers without having to think about it. Don’t go this route. First read, then think, then brainstorm together. Only then you can test in the interpreter.

It’s important that you truly understand the reasons behind the answers of all those tasks so that you can apply the same logic to other variables and other variable types.

Note that during interviews for Python positions, you will most likely have to answer to these type of questions.

All your answers should be only one line in a file. No space before or after the answer.

Resources

Read or watch:

• 9.10. Objects and values
• 9.11. Aliasing
• Immutable vs mutable types
• Mutation (Only this chapter)
• 9.12. Cloning lists
• Python tuples: immutable but potentially changing

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General

• Why Python programming is awesome
• What is an object
• What is the difference between a class and an object or instance
• What is the difference between immutable object and mutable object
• What is a reference
• What is an assignment
• What is an alias
• How to know if two variables are identical
• How to know if two variables are linked to the same object
• How to display the variable identifier (which is the memory address in the CPython implementation)
• What is mutable and immutable
• What are the built-in mutable types
• What are the built-in immutable types
• How does Python pass variables to functions

Requirements

Python Scripts

• Allowed editors: vi, vim, emacs
• All your files will be interpreted/compiled on Ubuntu 20.04 LTS using python3 (version 3.8.5)
• All your files should end with a newline character
• The first line of all your script files should be exactly #!/usr/bin/python3
• A README.md file, at the root of the folder of the project, is mandatory
• Your code should use the pycodestyle (version 2.8.*)
• All your files must be executable
• The length of your files will be tested using wc

.txt Answer Files

• Only one line
• No Shebang
• All your files should end with a new line

Tasks

0. Who am I?

What function would you use to get the type of an object?

Write the name of the function in the file, without ().

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 0-answer.txt

1. Where are you?

How do you get the variable identifier (which is the memory address in the CPython implementation)?

Write the name of the function in the file, without ().

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 1-answer.txt

2. Right count

In the following code, do a and b point to the same object? Answer with Yes or No.

>>> a = 89
>>> b = 100

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 2-answer.txt

3. Right count =

In the following code, do a and b point to the same object? Answer with Yes or No.

>>> a = 89
>>> b = 89

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 3-answer.txt

4. Right count =

In the following code, do a and b point to the same object? Answer with Yes or No.

>>> a = 89
>>> b = a

Repo:

GitHub repository: alx-higher_level_programming Directory: 0x09-python-everything_is_object

• File: 4-answer.txt

5. Right count =+

In the following code, do a and b point to the same object? Answer with Yes or No.

>>> a = 89
>>> b = a + 1

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 5-answer.txt

6. Is equal

What do these 3 lines print?

>>> s1 = "Best School"
>>> s2 = s1
>>> print(s1 == s2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 6-answer.txt

7. Is the same

What do these 3 lines print?

>>> s1 = "Best"
>>> s2 = s1
>>> print(s1 is s2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 7-answer.txt

8. Is really equal

What do these 3 lines print?

>>> s1 = "Best School"
>>> s2 = "Best School"
>>> print(s1 == s2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 8-answer.txt

9. Is really the same

What do these 3 lines print?

>>> s1 = "Best School"
>>> s2 = "Best School"
>>> print(s1 is s2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 9-answer.txt

10. And with a list, is it equal

What do these 3 lines print?

>>> l1 = [1, 2, 3]
>>> l2 = [1, 2, 3]
>>> print(l1 == l2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 10-answer.txt

11. And with a list, is it the same

What do these 3 lines print?

>>> l1 = [1, 2, 3]
>>> l2 = [1, 2, 3]
>>> print(l1 is l2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 11-answer.txt

12. And with a list, is it really equal

What do these 3 lines print?

>>> l1 = [1, 2, 3]
>>> l2 = l1
>>> print(l1 == l2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 12-answer.txt

13. And with a list, is it really the same

What do these 3 lines print?

>>> l1 = [1, 2, 3]
>>> l2 = l1
>>> print(l1 is l2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 13-answer.txt

14. List append

What does this script print?

l1 = [1, 2, 3]
l2 = l1
l1.append(4)
print(l2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 14-answer.txt

15. List add

What does this script print?

l1 = [1, 2, 3]
l2 = l1
l1 = l1 + [4]
print(l2)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 15-answer.txt

16. Integer incrementation

What does this script print?

def increment(n):
    n += 1

a = 1
increment(a)
print(a)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 16-answer.txt

17. List incrementation

What does this script print?

def increment(n):
    n.append(4)

l = [1, 2, 3]
increment(l)
print(l)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 17-answer.txt

18. List assignation

What does this script print?

def assign_value(n, v):
    n = v

l1 = [1, 2, 3]
l2 = [4, 5, 6]
assign_value(l1, l2)
print(l1)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 18-answer.txt

19. Copy a list object

Write a function def copy_list(l): that returns a copy of a list.

• The input list can contain any type of objects
• Your file should be maximum 3-line long (no documentation needed)
• You are not allowed to import any module

guillaume@ubuntu:~/0x09$ cat 19-main.py
#!/usr/bin/python3
copy_list = __import__('19-copy_list').copy_list

my_list = [1, 2, 3]
print(my_list)

new_list = copy_list(my_list)

print(my_list)
print(new_list)

print(new_list == my_list)
print(new_list is my_list)

guillaume@ubuntu:~/0x09$ ./19-main.py
[1, 2, 3]
[1, 2, 3]
[1, 2, 3]
True
False
guillaume@ubuntu:~/0x09$ wc -l 19-copy_list.py
3 19-copy_list.py
guillaume@ubuntu:~/0x09$

No test cases needed

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 19-copy_list.py

20. Tuple or not?

a = ()

Is a a tuple? Answer with Yes or No.

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 20-answer.txt

21. Tuple or not?

a = (1, 2)

Is a a tuple? Answer with Yes or No.

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 21-answer.txt

22. Tuple or not?

a = (1)

Is a a tuple? Answer with Yes or No.

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 22-answer.txt

23. Tuple or not?

a = (1, )

Is a a tuple? Answer with Yes or No.

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 23-answer.txt

24. Who I am?

What does this script print?

a = (1)
b = (1)
a is b

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 24-answer.txt

25. Tuple or not

What does this script print?

a = (1, 2)
b = (1, 2)
a is b

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 25-answer.txt

26. Empty is not empty

What does this script print?

a = ()
b = ()
a is b

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 26-answer.txt

27. Still the same?

>>> id(a)
139926795932424
>>> a
[1, 2, 3, 4]
>>> a = a + [5]
>>> id(a)

Will the last line of this script print 139926795932424? Answer with Yes or No.

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 27-answer.txt

28. Same or not?

>>> a
[1, 2, 3]
>>> id (a)
139926795932424
>>> a += [4]
>>> id(a)

Will the last line of this script print 139926795932424? Answer with Yes or No.

Repo: -GitHub repository: alx-higher_level_programming

• Directory: 0x09-python-everything_is_object
• File: 28-answer.txt

29. #pythonic

Write a function magic_string() that returns a string “BestSchool” n times the number of the iteration (see code):

• Format: see example
• Your file should be maximum 4-line long (no documentation needed)
• You are not allowed to import any module

guillaume@ubuntu:~/0x09$ cat 100-main.py
#!/usr/bin/python3
magic_string = __import__('100-magic_string').magic_string

for i in range(10):
    print(magic_string())

guillaume@ubuntu:~/0x09$ ./100-main.py | cat -e
BestSchool$
BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool, BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool$
BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool, BestSchool$
guillaume@ubuntu:~/0x09$ wc -l 100-magic_string.py
4 100-magic_string.py
guillaume@ubuntu:~/0x09$

No test cases needed

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 100-magic_string.py

30. Low memory cost

Write a class LockedClass with no class or object attribute, that prevents the user from dynamically creating new instance attributes, except if the new instance attribute is called first_name.

• You are not allowed to import any module

guillaume@ubuntu:~/0x09$ cat 101-main.py
#!/usr/bin/python3
LockedClass = __import__('101-locked_class').LockedClass

lc = LockedClass()
lc.first_name = "John"
try:
    lc.last_name = "Snow"
except Exception as e:
    print("[{}] {}".format(e.__class__.__name__, e))

guillaume@ubuntu:~/0x09$ ./101-main.py
[AttributeError] 'LockedClass' object has no attribute 'last_name'
guillaume@ubuntu:~/0x09$

No test cases needed

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 101-locked_class.py

31. int 1/3

julien@ubuntu:/python3$ cat int.py
a = 1
b = 1
julien@ubuntu:/python3$

Assuming we are using a CPython implementation of Python3 with default options/configuration:

• How many int objects are created by the execution of the first line of the script? (103-line1.txt)
• How many int objects are created by the execution of the second line of the script (103-line2.txt)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 103-line1.txt, 103-line2.txt

32. int 2/3

julien@ubuntu:/python3$ cat int.py
a = 1024
b = 1024
del a
del b
c = 1024
julien@ubuntu:/python3$

Assuming we are using a CPython implementation of Python3 with default options/configuration:

• How many int objects are created by the execution of the first line of the script? (104-line1.txt)
• How many int objects are created by the execution of the second line of the script (104-line2.txt)
• After the execution of line 3, is the int object pointed by a deleted? Answer with Yes or No (104-line3.txt)
• After the execution of line 4, is the int object pointed by b deleted? Answer with Yes or No (104-line4.txt)
• How many int objects are created by the execution of the last line of the script (104-line5.txt)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 104-line1.txt, 104-line2.txt, 104-line3.txt, 104-line4.txt, 104-line5.txt

33. int 3/3

julien@twix:/tmp/so$ cat int.py
print("I")
print("Love")
print("Python")
julien@ubuntu:/tmp/so$

Assuming we are using a CPython implementation of Python3 with default options/configuration:

• Before the execution of line 2 (print("Love")), how many int objects have been created and are still in memory? (105-line1.txt)
• Why? (optional blog post :))

Hint: NSMALLPOSINTS, NSMALLNEGINTS

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 105-line1.txt

34. Clear strings

guillaume@ubuntu:/python3$ cat string.py
a = "SCHL"
b = "SCHL"
del a
del b
c = "SCHL"
guillaume@ubuntu:/python3$

Assuming we are using a CPython implementation of Python3 with default options/configuration (For answers with numbers use integers, don’t spell out the word):

• How many string objects are created by the execution of the first line of the script? (106-line1.txt)
• How many string objects are created by the execution of the second line of the script (106-line2.txt)
• After the execution of line 3, is the string object pointed by a deleted? Answer with Yes or No (106-line3.txt)
• After the execution of line 4, is the string object pointed by b deleted? Answer with Yes or No (106-line4.txt)
• How many string objects are created by the execution of the last line of the script (106-line5.txt)

Repo:

• GitHub repository: alx-higher_level_programming
• Directory: 0x09-python-everything_is_object
• File: 106-line1.txt, 106-line2.txt, 106-line3.txt, 106-line4.txt, 106-line5.txt