๐Ÿ“’ Today I Learn/๐Ÿ Python

์•Œ๋ฉด ์œ ์šฉํ•œ ํŒŒ์ด์ฌ ๋ฌธ๋ฒ• (2) ๋ฆฌ์ŠคํŠธ ์ปดํ”„๋ฆฌํ—จ์…˜, lambda

ny:D 2024. 5. 7. 16:32

๋ฆฌ์ŠคํŠธ ์ปดํ”„๋ฆฌํ—จ์…˜

๐Ÿ’ก ๋ฆฌ์ŠคํŠธ ์ปดํ”„๋ฆฌํ—จ์…˜ :  ํŒŒ์ด์ฌ์—์„œ ๋ฆฌ์ŠคํŠธ๋ฅผ ๊ฐ„๊ฒฐํ•˜๊ฒŒ ์ƒ์„ฑํ•˜๋Š” ๋ฐฉ๋ฒ• 
# ๊ธฐ๋ณธ์ ์ธ ๊ตฌ์กฐ
[ํ‘œํ˜„์‹ for ํ•ญ๋ชฉ in iterable if ์กฐ๊ฑด๋ฌธ]
  • ํ‘œํ˜„์‹ :  ๊ฐ ํ•ญ๋ชฉ์— ๋Œ€ํ•œ ๊ณ„์‚ฐ์ด๋‚˜ ๋ณ€ํ™˜
  • ํ•ญ๋ชฉ :  ๋ฐ˜๋ณต๋˜๋Š” ๊ฐ’
  • iterable : ๋ฐ˜๋ณต ๊ฐ€๋Šฅํ•œ ๊ฐ์ฒด

์˜ˆ์‹œ 1) 1๋ถ€ํ„ฐ 10๊นŒ์ง€์˜ ์ˆซ์ž๋ฅผ ์ œ๊ณฑํ•œ ๋ฆฌ์ŠคํŠธ ์ƒ์„ฑ

squares = [x**2 for x in range(1, 11)]
print(squares)  

## ์ถœ๋ ฅ: [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
  • `range(1,11)`: 1๋ถ€ํ„ฐ 10๊นŒ์ง€ ์ž์—ฐ์ˆ˜๋ฅผ
  • `for x `: x ๋กœ ๋ฐ›์•„์„œ
  • `x**2`: ์ œ๊ณฑ

์˜ˆ์‹œ 2) ๋ฆฌ์ŠคํŠธ ์ปดํ”„๋ฆฌํ—จ์…˜์„ ์ค‘์ฒฉํ•˜์—ฌ 2์ฐจ์› ๋ฆฌ์ŠคํŠธ ์ƒ์„ฑ

matrix = [[i for i in range(1, 4)] for j in range(3)]
print(matrix)  
## ์ถœ๋ ฅ: [[1, 2, 3], [1, 2, 3], [1, 2, 3]]
  • `range(1,4)`: 1๋ถ€ํ„ฐ 3๊นŒ์ง€ ์ž์—ฐ์ˆ˜๋ฅผ
  • `i for i`: i๋กœ ๋ฐ›์•„์„œ i๋กœ ์ถœ๋ ฅํ•œ ๊ฒƒ์„
  • `range(3)`: 3๋ฒˆ ๋ฐ˜๋ณตํ•˜๊ธฐ

์˜ˆ์‹œ 3) if , else ์กฐ๊ฑด๋ฌธ

[์ถœ๋ ฅ๊ฐ’ if ์กฐ๊ฑด else ์กฐ๊ฑด ๋งŒ์กฑ x์‹œ ์ถœ๋ ฅ๊ฐ’ for i in ๋ฐ˜๋ณตํ•  ๊ฐ’]

if ์กฐ๊ฑด๋ฌธ์€ ์„ ํƒ์ ์œผ๋กœ ์‚ฌ์šฉ๋  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์กฐ๊ฑด์ด ์ฐธ์ผ ๋•Œ๋งŒ ํ•ด๋‹น ํ•ญ๋ชฉ์„ ๊ฒฐ๊ณผ ๋ฆฌ์ŠคํŠธ์— ์ถ”๊ฐ€

Lambda

๐Ÿ’ก Lambda :  ์ต๋ช… ํ•จ์ˆ˜๋กœ, ์ด๋ฆ„ ์—†์ด ์ •์˜๋˜๋Š” ๊ฐ„๋‹จํ•œ ํ•จ์ˆ˜
์ฃผ๋กœ ํ•œ ์ค„๋กœ ํ‘œํ˜„๋˜๋ฉฐ, ์ผ๋ฐ˜์ ์ธ ํ•จ์ˆ˜ ์ •์˜์™€๋Š” ๋‹ฌ๋ฆฌ def ํ‚ค์›Œ๋“œ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š๊ณ  lambda ํ‚ค์›Œ๋“œ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ์ •์˜
lambda ๋งค๊ฐœ๋ณ€์ˆ˜ : ๊ณ„์‚ฐ์‹

์˜ˆ์‹œ 1) ์ œ๊ณฑ ํ•จ์ˆ˜

square = lambda x: x ** 2
print(square(4))  
## ์ถœ๋ ฅ: 16

→ ๋งค๊ฐœ๋ณ€์ˆ˜ x์— ๋Œ€ํ•˜์—ฌ ์ œ๊ณฑํ•˜๊ธฐ(`x**2`)

 

์˜ˆ์‹œ 2) lambda & filter

๐Ÿ’ก filter
filter(์กฐ๊ฑด ํ•จ์ˆ˜, ๋ฐ˜๋ณต ๊ฐ€๋Šฅํ•œ ๋ฐ์ดํ„ฐ)
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers = list(filter(lambda x: x % 2 == 0, numbers))
print(even_numbers)  
## ์ถœ๋ ฅ: [2, 4, 6, 8, 10]

 

  • ์กฐ๊ฑดํ•จ์ˆ˜ ์ž๋ฆฌ์— `lambda x: x%2 == 0`์ด ๋“ค์–ด๊ฐ (์กฐ๊ฑด : x๊ฐ€ ์ง์ˆ˜์ผ ๋•Œ)
  • ๋ฐ˜๋ณต ๊ฐ€๋Šฅํ•œ ๋ฐ์ดํ„ฐ = numbers
    → numbers์—์„œ x๊ฐ€ ์ง์ˆ˜์ธ ๊ฒฝ์šฐ๋ฅผ even_numbers๋ผ๋Š” ๋ฆฌ์ŠคํŠธ๋กœ ๋ฐ˜ํ™˜ํ•˜๊ธฐ

์˜ˆ์‹œ 3)  lambda & map

๐Ÿ’ก map
map(ํ•จ์ˆ˜, ๋ฐ˜๋ณต ๊ฐ€๋Šฅํ•œ ๋ฐ์ดํ„ฐ)
numbers = [1, 2, 3, 4, 5]
squared_numbers = list(map(lambda x: x ** 2, numbers))
print(squared_numbers)  
## ์ถœ๋ ฅ: [1, 4, 9, 16, 25]
  • ํ•จ์ˆ˜ ์ž๋ฆฌ์— `lambda x: x**2`๊ฐ€ ๋“ค์–ด๊ฐ (x๋ฅผ ์ œ๊ณฑํ•ด์ฃผ๋Š” ํ•จ์ˆ˜)
  • ๋ฐ˜๋ณต ๊ฐ€๋Šฅํ•œ ๋ฐ์ดํ„ฐ = numbers
    → numbers์— ์žˆ๋Š” ๋ชจ๋“  ๊ฐ’๋“ค์— ๋Œ€ํ•ด ์ œ๊ณฑํ•ด ์ด๋ฅผ squared_numbers๋ผ๋Š” ๋ฆฌ์ŠคํŠธ๋กœ ๋ฐ˜ํ™˜ํ•˜๊ธฐ