파이썬 자주 사용하는 라이브러리 모음 - 코테 꿀팁

 

1. math

import math

print(math.factorial(5)) # 5! = 120
print(math.gcd(36, 60))  # 최대공약수(GCD) = 12
print(math.sqrt(25))     # 제곱근 = 5.0
print(math.ceil(3.1))    # 올림 = 4
print(math.floor(3.9))   # 내림 = 3

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2. itertools

import itertools

arr = [1, 2, 3]

# 순열 (3개 중 2개를 선택하는 모든 경우) -> 순서 의미 있음
print(list(itertools.permutations(arr, 2)))
#[(1, 2), (1, 3), (2, 1), (2, 3), (3, 1), (3, 2)]

# 조합 (3개 중 2개를 뽑는 경우) -> 순서 의미 없음
print(list(itertools.combinations(arr, 2)))
#[(1, 2), (1, 3), (2, 3)]

# 중복 조합
print(list(itertools.combinations_with_replacement(arr, 2)))
# [(1, 1), (1, 2), (1, 3), (2, 2), (2, 3), (3, 3)]

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3. collections

deque

from collections import deque

dq = deque([1, 2, 3])
dq.append(4)	  # 오른쪽 추가
dq.appendleft(0)  # 왼쪽 추가
print(dq)         # deque([0, 1, 2, 3, 4])

dq.pop()		  # 오른쪽 제거
dq.pop(left)	  # 왼쪽 제거
print(dq)		  # deque([1, 2, 3])

 

Counter

from collections import Counter

arr = ['a', 'b', 'c', 'a', 'b', 'a']
counter = Counter(arr)
print(counter)			# Counter({'a': 3, 'b': 2, 'c': 1})
print(counter['a'])		# 3
print(counter.most_common(1))	# [('a', 3)]

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4. heapq

 

최소 힙(기본)

import heapq

heap = []
heapq.heappush(heap, 3)
heapq.heappush(heap, 1)
heapq.heappush(heap, 4)

print(heapq.heappop(heap))	# 1
print(heapq.heappop(heap))	# 3

 

 

최대 힙

heap = []
heapq.heappush(heap, -3)
heapq.heappush(heap, -1)
heapq.heappush(heap, -4)

print(-heapq.heappop(heap))	# 4
print(-heapq.heappop(heap))	# 3

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5. bisect (이진탐색)

import bisect

arr = [1, 2, 4, 4, 5, 6]
print(bisect.bisect_left(arr, 4))	# 2 (4가 처음 등장하는 인덱스)
print(bisect.bisect_right(arr, 4))	# 4 (4가 끝나는 위치)

# 값 삽입
bisect.insort(arr, 3)
print(arr)	# [1, 2, 3, 4, 5, 5, 6]

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6. functools

lru_cach(메모이제이션)

from functools import lru_cache

@lru_cache(None)
def fib(n):
	if n <= 1:
    	return n
    return fib(n - 1) + fib(n - 2)
    
print(fib(50))

 

 

 

 

 

 

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