yield 사용법

# 리스트를 만들어서 던짐

 

def squareList(nums):

result = []

for n in nums: result.append(n * n)

return result

 

myNums = squareList([1, 2, 3, 4, 5])

 

print(myNums)

 

# 결과

[1, 4, 9, 16, 25]

 

# yield를 사용해 객체를 던짐

 

def squareList(nums):

for n in nums: yield (n * n)

 

myNums = squareList([1, 2, 3, 4, 5])

 

for n in myNums:

print(n, end = ' ')

 

# 결과

1 4 9 16 25

 

 

# flatten list

nested_ls = [[1, 2], [3, 4], [5]]

 

def flatten(nested):

for sublist in nested:

for ele in sublist:

yield ele

 

o = flatten(nested_ls)

print(list(o))

 

# 결과

[1, 2, 3, 4, 5]

 

 

# flatten list with comprehension, generator

 

nested_ls = [[1, 2], [3, 4], [5]]

flat = (x for sublist in nested_ls for x in sublist)

 

print(list(flat))

 

# 결과

[1, 2, 3, 4, 5]

 

 

# flatten multiple list

def flatten_smart(nested):

try:

for sublist in nested:

for ele in flatten_smart(sublist):

yield ele

except TypeError:

yield nested

 

nested_ls = [[[1], 2], 3, 4, [5, [6, 7]], 8]

 

o = flatten_smart(nested_ls)

print(list(o))

 

# 결과

[1, 2, 3, 4, 5, 6, 7, 8]

 

# Consider generators instead of returning lists
def index_words(text: str) -> list[str]:
    result: list[str] = []
    if text:
        result.append(0) # first position
    for idx, letter in enumerate(text):
        if letter == ' ':
            result.append(idx + 1)
    return result

address: str = "Four score and evene years ago our fathers brought forth on this continent a new nation, conceived in liberty, and dedicated to the proposition that all men are created equal."
# result: list[int] = index_words(address)
# print(result[:3])
# print(result)
 
# generator version of the function
# 리스트는 리턴하는 것보다 제너레이터로 구현하는 것이 깔끔하기는 하다.
# 매우 많은 데이터를 하나의 리스트에 넣는 과정이 메모리 소모가 심할 수 있다.
def index_words_gr(text):
    if text:
        yield 0
    for idx, letter in enumerate(text):
        if letter == ' ':
            yield idx + 1

it = index_words_gr(address)
print(list(it))

# 결과
[0, 5, 11, 15, 21, 27, 31, 35, 43, 51, 57, 60, 65, 75, 77, 81, 89, 99, 102, 111, 115, 125, 128, 132, 144, 149, 153, 157, 161, 169]

 

from typing import Generator

def get_even(nums: list[int]) -> Generator [int]:
    for num in nums:
        if num % 2 == 0:
            yield num

nums: list[int] = [n for n in range(1, 101)]
even_gen = get_even(nums)

print(list(even_gen))

# 결과
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100]