Basic

為了可讀性 1000與1_000一致
int( … , 2)
將… 轉2為底的int
合併
[1]+[1] == [1,1]
zip
a, b = [1,2,3], [4,5,6]
print(list(zip(a,b)))

[(1, 4), (2, 5), (3, 6)]
count += (sum(edges) >= 1)
True+True == 2
賦值
x, y, d = q.popleft() 或 for a, b in (…)
pop 出來分給x,y,d
- for i, j in enumerate(…)
  [[i0, j0], [i1, j1], …]
copy
import random, copy
change = copy.deepcopy(self.nums)
random.shuffle(change)
在新生陣列打亂順序
反轉
[::-1]
if l < mid >r:
mid >l && r
if mid < len(nums) -1 else float(‘-inf’)
inf
@lru_cache(maxsize=None)
寫在def上方，暫存重用值，time() 或 random() 變動函數前沒有意義，maxsize 默認 128，如果 maxsize 設為 None，LRU 特性將被禁用且緩存可無限增長
全域變數
global a,b
a,b = 1,2
“”.join(sum(res, []))
[[1],[2],[3],[4]] => [1,2,3,4]
拆包

a = [[1],[2],[3],[4]]
print(*a) # [1] [2] [3] [4]

a = [1,2,3]
print(*a) # 1,2,3

a = [[1,2,3],[4,5,6]]  
print(*a) # [1,2,3],[4,5,6]

Loop

走訪陣列
for _ in range(n):
走訪串列
fast = llst.head
while fast and fast.next:
fast = fast.next
for(while):…else:
沒有在for中被break，順利執行完就跑else區塊
取值

def foo(param1, *param2):
    print(param1)
    print(param2)

def bar(param1, **param2):
    print(param1)
    print(param2)

 foo(1,2,3,4,5)
 bar(1,a=2,b=3)
 >
1
(2, 3, 4, 5)
1
{'a': 2, 'b': 3}

Product 3Ｘ3

from itertools import product 
for i, j in product(range(0,3),range(0,3)):  
    print(i,j)  
>
0 0
0 1
0 2
1 0
1 1
1 2
2 0
2 1
2 2

從最長開始排序

words = {"able","ale","apple","bale","kangaroo"}
for word in sorted(words, key=len, reverse=True):
    print(word)
>
kangaroo
apple
able
bale
ale

Comprehension

… if … else …
if, else，沒有：

age_group = "Minor" if age < 18 else "Adult"
==

if age < 18:
    age_group = "Minor"
else:
    age_group = "Adult"

… if … else … if … else …
if, elif, else，沒有：

board[i][j] = 'X' if board[i][j] == 'O' else 'O' if board[i][j] == 'S' else board[i][j] 
==

if board[i][j] == 'O':
    board[i][j] = 'X'
elif board[i][j] == 'S':
    board[i][j] = 'O'
else:
    board[i][j]

[int(i)**2 for i in str(n)]
從n取各值為i，轉int後平方再展開

function

class Account:
    def __init__(self, number, name):
        self.number = number
        self.name = name
        self.balance = 0
    def deposit(self, amount):
	    ...
a = Account('E122', 'Justin')
a.deposit(-1)

Assert

AssertionError: 印出失敗訊息，並不會進行後續動作

assert <條件>, <條件失敗訊息>


if x > 0:
    # do some
    ...
else:
    assert x == 0, 'x 不會是負數' # AssertionError: x 不會是負數
    # do other
    ...

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