Number vs. String

Int, float, complex vs. 문자열

Built-in Collections

{set} vs. {: Dictionary}

Set	Dictionary
key값만 있는	key,value 값이 있다.
가변(mutable) 리스트형	– key값은 immutable(변경 불가)형식이어야 하고, – value값은 mutable(변경 가능) 형식도 가능하다
unordered collection of data	unordered collection of data that stores data in key-value pairs.

---

(Tuple) vs. [List]

Tuple	List
immutable	mutable
수정이 불가능하다. an ordered collection of data.	수정이 가능함 (ex. list.append() ) collection of ordered data.

methods

#=== Using list slicing
### Extract sublists with list slicing
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
first_five = numbers[:5]
last_five = numbers[5:]
middle_five = numbers[3:8]
evens = numbers[1::2]
odds = numbers[::2]
reversed_numbers = numbers[::-1]

#=== Using string slicing
### Extract substrings with string slicing
name = 'Alice'
first_three = name[:3]
last_three = name[2:]
middle_three = name[1:4]
evens = name[1::2]
odds = name[::2]
reversed_name = name[::-1]

#=== Using list unpacking
### Unpack lists with list unpacking
numbers = [1, 2, 3]
a, b, c = numbers

#=== Using dictionary unpacking
### Unpack dictionaries with dictionary unpacking
person = {'name': 'Alice', 'age': 24}
name, age = person.values()

#=== Using set unpacking
### Unpack sets with set unpacking
numbers = {1, 2, 3}
a, b, c = numbers

#=== Using f-string
### Format strings with f-string
name = 'Alice'
age = 24
formatted_string = f'My name is {name} and I am {age} years old.'

name = 'Alice'
name_upper = name.upper()
name_lower = name.lower()
name_title = name.title()
name_capitalize = name.capitalize()
name_swapcase = name.swapcase()
name_strip = name.strip()
name_lstrip = name.lstrip()
name_rstrip = name.rstrip()
name_replace = name.replace('A', 'Z')
name_split = name.split('l')
name_join = '-'.join(['A', 'l', 'i', 'c', 'e'])

slicing

#=== Using sets to store unique values 
### fileter distinct value, Set은 unordered key값만 있는 dictionary
numbers = [2, 1, 1, 1, 2, 3, 3, 4, 5, 6, 7, 8, 5, 5]
numbers = set(numbers)     #  {1, 2, 3, 4, 5, 6, 7, 8}

june_dates = [datetime(2024, 6, day) for day in range(1, 31)]
random_dates = random.sample(june_dates, k=16)  # unordered dates, unique
random_dates = random.choices(june_dates, k=16)  # unordered dates, un-unique
my_dates = set(random_dates)

numbers.add(11)
numbers.discard(5)

numbers.remove(6)     # 없는 값을 지우려고 하면 에러 발생
numbers.clear()

#=== Using list methods
### Manipulate lists with list methods
numbers = [1, 2, 3, 4, 5]
numbers.append(6)
numbers.insert(0, 0)
numbers.extend([7, 8, 9])
numbers.pop(0)
numbers.sort()

numbers.remove(0)
numbers.clear()

#=== Using dictionary methods
### Manipulate dictionaries with dictionary methods
person = {'name': 'Alice', 'age': 24}
person['name'] = 'Bob'
person['age'] = 50
person['city'] = 'New York'
person.pop('city')
person.popitem()
person.clear()

Immutable vs. Mutable

 변수가 담고 있는 object의 속성에 따라 결정

Immutable	mutable
int, float, bool, string, tuple	list, dictionary

 json vs. dictionary

json과 dictionary 모두 KEY, VALUE인데 왜 굳이 json 일까

Dictionary	JSON
Data Structure	Data Format
key는 어떤거든지… (key기본값 없음)	key는 항상 String (key기본값 undefined)
True/ False / None	true/ false/ null

import json

dictVal = {'name':'johnDou', 'age':16, 'job':True}

jsonVal = json.dumps(dictVal)
# '{"name": "johnDou", "age": 16, "job": true}'

dictVal2 = json.loads(jsonVal)
# {'name': 'johnDou', 'age': 16, 'job': True}

dictVal['name']
# 'johnDou'
jsonVal['name']
# TypeError: string indices must be integers