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1^st Assignment!

Assignment #1: Write your introduction and submit PR

Deadline: 11:59 PM at Sep 16^th (1 week)
Practice your Git and GitHub
Feel free to react each other’s introduction (that’s also review!)
Repository: https://github.com/HUFS-LAI-Seungtaek/HUFS-LAI-OOP-2025-2
Follow the instructions in https://github.com/HUFS-LAI-Seungtaek/HUFS-LAI-OOP-2025-2/tree/main/assignments/assignment1

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Git/GitHub Basics�(Or, How to Submit Assignment)

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What is Git?

Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.

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What is GitHub?

GitHub is a cloud-based platform built on the "Git" version control system that provides tools for developers to store, manage, share, and collaborate on code and other files.

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Git & GitHub?

git: version control & code management (local)
github: code storage (cloud)
push: upload code to github

push

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Components of Git: Repository

Repository is a version-controlled project space that stores your files, branches, and full change history.

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Components of Git: Branch

Branch is an independent line of development – a named timeline of commits within a repo.

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Components of Git: Commit

Commit is a saved snapshot of changes with a message, author, and timestamp.

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Git Branching Structure (Dev)

src: https://docs.symbol.dev/handbook/git-branching.html

branch

commit

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Git Branching Structure (Ours)

main

HUFS-LAI-Seungtaek/HUFS-LAI-OOP-2025-2:main

hufs-student-2/HUFS-LAI-OOP-2025-2:main

main+1

assignment1.py

main+2

assignment1.py

main+2

main+1

main

hufs-student-1/HUFS-LAI-OOP-2025-2:main

main+1

assignment1.py

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Git Workflow

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Git Workflow

Repository structure:

upstream (professor:main): original repo
origin (student:main): your repo
local: your computer

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Git Workflow: fork

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Git Workflow: clone

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Git Workflow: add & commit

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Git Workflow: add & commit

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Git Workflow: add & commit

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Git Workflow: add & commit

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Git Workflow: add & commit

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Git Workflow: push

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Git Workflow: PR & merge

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Git Workflow: branch

For your assignment, no need to use `branch`

professor:main (remote) 🡪 fork
student:main (remote) 🡪 clone
student:main (local) 🡪 commit
student:main+1 (local) 🡪 commit
student:main+2 (local) 🡪 push
student:main+2 (remote) 🡪 PR
professor:main+1 (remote)

It’s not about remote vs. local.
It’s about w/ permission vs. w/o permission.

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Git Workflow: branch

In your team’s repo, if you are not allowed to push `main` branch, …

student:main (remote) 🡪 clone
student:main (local) 🡪 checkout (In this case, $ git checkout –b feature)
student:feature (local) 🡪 commit
student:feature+1 (local) 🡪 commit
student:feature+2 (local) 🡪 push
student:feature+2 (remote) 🡪 PR
student:main+1 (remote)

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GitHub Web Shortcuts �(Or, How to Submit Assignment #1)

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Fork repository

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Fork repository

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Repo is copied under your account.

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Add a file

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Add a file

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Add a file

members/{학생이름}.md

Example: members/seungtaek.md

Example: members/yeachan.md

Example: members/gildong.md

Don’t include {}�Don’t use uppercase

Don’t use Korean

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Introduce yourself

You can see actual “code” from

https://github.com/HUFS-LAI-Seungtaek/HUFS-LAI-OOP-2025-2/blob/main/members/seungtaek.md?plain=1

Feel free to introduce yourself more!

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Commit the change (your file)

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Back to “your” repo

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Submit PR to lecture repository

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Submit PR to lecture repository

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Submit PR to lecture repository

Please follow the format �n-th Assignment by {학번} ({Full name})

Do not use ‘ or “

Please use ` (look at the ~)

You can see the preview.

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Python Basics (2)

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Comments (1)

You can use “#”

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Comments (2)

You can use multiple line comments with (""")

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Data Types (1)

Why data types matter?

Define what kind of data a variable can store
Determine what operations can be performed
Affect memory usage and performance
Ensure data integrity in your programs

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Data Types (2)

Built-in data types (not full list)

Text type: str
Numeric types: int, float
Sequence types: list, tuple
Mapping type: dict
Set types: set
Boolean type: bool
None type: None

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Data Types (3)

Mutable

list
dict
set

Immutable

Text type: str
Numeric types: int, float
Sequence types:, tuple
…

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Data Types (3)

Text type: str

Definition: Immutable sequence of Unicode characters
Common operators: + (concatenation), * (repeat), [] (index), [:] (slice)

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Q0: “How to Change Pithon to Python?”

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Q0: “How to Change Pithon to Python?”

A0:

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Data Types (4)

Numeric types: int, float

Definition: Integer (int) and floating-point (float) numbers
Common operators: +, -, *, /, // (floor division), % (modulus), ** (power)

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Data Types (5)

Sequence types: list, tuple

Definition: Ordered collections (list is mutable, tuple is immutable)
Common operators: + (concatenate), * (repeat), [] (index), [:] (slice), in (membership)

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Q1: “Why list in tuple is changed?”

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Q1: “Why list in tuple is changed?”

A1: “It’s about reference immutability.”

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Q2: “Why does changing y also change x?”

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Q2: “Why does changing y also change x?”

A2: “It’s about reference copy.”

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Data Types (6)

Mapping type: dict

Definition: Key-value pairs, mutable, keys are unique
Common operators: in (check key), [] (access value), .keys(), .values(), .items()

The most adorable feature of Python for me.

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Data Types (7)

Set type: set

Definition: Unordered collection of unique elements
Common operators: | (union), & (intersection), - (difference), ^ (symmetric difference)

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Q3: “Why is dict + dict not allowed?”

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Q3: “Why is dict + dict not allowed?”

A3: “Explicit is better than implicit.”

ref: https://peps.python.org/pep-0020/

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Be explicit (b will overwrite a)

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Data Types (8)

Boolean type: bool

Definition: Logical values True or False
Common operators: and (&), or (|), not

More Pythonic

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Data Types (9)

None type: None

Definition: Represents “no value” or “null” (= “nothing here”)
Common operators: is, is not

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String Format

%s: string
%c: character (or integer interpreted as Unicode code point)
%d: integer (decimal)
%f: floating-point (decimal form)
%o: octal (base 8) integer
%x: hexadecimal (base 16) integer
%%: literal %

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String Format

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Indexing and Slicing

Negative indexing

s[-1]: last element
s[-2]: second last element

Slicing with Step

s[start:end:step]
s[::]: copy (normal order)
s[::2]: every second element
s[::-1]: reversed

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String Built-in Functions (1)

Counting & Searching

.count(sub) 🡪 count occurrences
.find(sub) 🡪 return index, -1 if not found
.index(sub) 🡪 return index, error if not found

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String Built-in Functions (2)

Transformation

.upper() / .lower() 🡪 change case (new string)
.replace(old, new) 🡪 replace substring
.join(iterable) 🡪 insert string between elements

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String Built-in Functions (3)

Whitespace Handling & Splitting

.lstrip() / .rstrip() / .strip() 🡪 remove spaces
.split([sep]) 🡪 split into list

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String Built-in Functions (4)

Checks

.isalpha() 🡪 only letters?
.isdigit() 🡪 only digits?
.startswith(sub) / .endswith()

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Useful List Functions (1)

Functions

.append() 🡪 add element at end
.sort() 🡪 sort ascending
.reverse() 🡪 reverse order
.index(x) 🡪 return index of first occurrence

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Useful List Functions (2)

Functions

.insert(i, x) 🡪 insert at position
.remove(x) 🡪 remove first occurrence
.pop([i]) 🡪 pop element (last or at index)
.count(x) 🡪 count occurrences
.extend(list) 🡪 extend with another list

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if Statements

Programs make decisions based on conditions.
Indentation is part of the syntax (use 4 spaces; do not mix tabs/spaces).
A colon : follows if / elif / else.

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if Statements

Logical operators & short-circuit
and, or, not (short-circuit evaluation)

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if Statements

elif for multiple branches

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if Statements

Math-style chaining improves readability

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if Statements

Conditional expression (ternary)
Form: A if condition else B

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if Statements

Do nothing with pass

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if Statements

Blank list is falsy (not actually False).

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while Loops

Repeats block while condition is True.
Ends when condition becomes False.

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while Loops

break exists loop immediately.

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while Loops

continue jumps back to condition check.

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while Loops

else executes only if loop ended normally (not by break).

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for Loops

Iterates directly over elements of a sequence (list, tuple, string, etc.).
No need for index counters unless explicitly needed.

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for Loops

enumerate returns index + value.

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for Loops

zip iterates multiple lists together.

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for Loops

continue skips the rest of the loop body and jumps to the next iteration.

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for Loops

range generates arithmetic sequences.

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for Loops

Example of nested loops (multiplication table)

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for Loops

break exists loop immediately.
else runs only if loop terminates normally (no break).

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List Comprehensions

Concise syntax to build lists.

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Function

A function maps inputs to an output after performing a task.
Why?

Reuse: avoid repeating code
Clarity: structure programs by tasks
Testability: small, composable units

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Function

Syntax

def + name + parameters
return sends the result (and exits the function)

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Function

Parameters vs. Arguments

Parameters: variables in the function definition
Arguments: actual values passed at call site

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Function

Four shapes (inputs/return)

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Function

Calling with keywords

Call by name, order doesn’t matter

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Function

Variable-length arguments

*args: collect extra positional args (tuple)
**kwargs: collect keyword args (dict)

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Function

Function returns always one object

You can return multiple values via a tuple
First return encountered ends the function.

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Function

Default parameters (and order)

Defaults must come after non-defaults

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Function

Scope & side effects

Parameters are local to the function

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Function

Scope & side effects

Prefer returning the new value

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Function

Scope & side effects

global exists but avoid (hurts modularity)

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Function

Mutable objects can be modified in place.

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Function

lambda: one-line anonymous functions

It is great as small callbacks / key functions.

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Function

Document your function right under the def

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Function

Early return to exit on special cases

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Function

Combine *args with a mode

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User & File I/O

User I/O: input(), print()
File I/O: open(), read/write, close()
Why important?

Most programs take input & product output
Need persistence beyond one run 🡪 files

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User & File I/O

User input/output

input() 🡪 always string, convert with int(), float()
print() 🡪 sep, end customize formatting

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User & File I/O

Basic file writing/reading

Modes: ‘r’ read, ‘w’ write (overwrite), ‘a’ append
encoding=“utf-8”: avoid mojibake (한글 깨짐 방지)

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User & File I/O

Reading variants (memory vs. streaming)

reads() loads all 🡪 risky on huge files
Iteration (for line in f) reads chunk by chunk 🡪 scalable

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User & File I/O

Why with matters

Auto-close file even if error occurs
Common pitfalls without with:

Forgetting close() 🡪 locked file, lost data
Writing without encoding 🡪 OS-dependent behavior

With-block != new scope (Python has function scope, not block scope)

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