Python -- 讓你的代碼運行的更快的技巧
平臺
運行測試的平臺環境：
>>> importsys
>>> importplatform
>>> platform.system()
'Linux'
>>> platform.release()
'3.11.0-19-generic'
>>> sys.version
'2.7.5+ (default, Feb 27 2014, 19:37:08)
[GCC 4.8.1]'
>>> fromtimeitimporttimeit
>>> fromdisimportdis
>>>
以下的代碼主要是使用了 timeit 函數測試處理時間，以及使用 dis 函數顯示詳細的處理步驟（匯編的方式），能讓你清楚的知道，慢在哪里？為什么慢？
測試用例 1
更快的方式：
def a():
d = {}
return d
>>>
>>> timeit(a, number=1000000)
... 0.0905051231384
>>>
>>> dis(a)
5 0 BUILD_MAP 0
3 STORE_FAST 0 (d)
6 6 LOAD_FAST 0 (d)
9 RETURN_VALUE
>>>
更慢的方式：
def a():
d = dict()
return d
>>>
>>> timeit(a, number=1000000)
... 0.206549167633
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (dict)
3 CALL_FUNCTION 0
6 STORE_FAST 0 (d)
6 9 LOAD_FAST 0 (d)
12 RETURN_VALUE
>>>
測試用例 2
更快的方式：
def a():
l = [0, 8, 6, 4, 2, 1, 3, 5, 7, 9]
l.sort()
return l
>>>
>>> timeit(a, number=1000000)
... 0.53688287735
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (0)
3 LOAD_CONST 2 (8)
6 LOAD_CONST 3 (6)
9 LOAD_CONST 4 (4)
12 LOAD_CONST 5 (2)
15 LOAD_CONST 6 (1)
18 LOAD_CONST 7 (3)
21 LOAD_CONST 8 (5)
24 LOAD_CONST 9 (7)
27 LOAD_CONST 10 (9)
30 BUILD_LIST 10
33 STORE_FAST 0 (l)
6 36 LOAD_FAST 0 (l)
39 LOAD_ATTR 0 (sort)
42 CALL_FUNCTION 0
45 POP_TOP
7 46 LOAD_FAST 0 (l)
49 RETURN_VALUE
>>>
更慢的方式：
def a():
l = [0, 8, 6, 4, 2, 1, 3, 5, 7, 9]
return sorted(l)
>>>
>>> timeit(a, number=1000000)
... 0.781757831573
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (0)
3 LOAD_CONST 2 (8)
6 LOAD_CONST 3 (6)
9 LOAD_CONST 4 (4)
12 LOAD_CONST 5 (2)
15 LOAD_CONST 6 (1)
18 LOAD_CONST 7 (3)
21 LOAD_CONST 8 (5)
24 LOAD_CONST 9 (7)
27 LOAD_CONST 10 (9)
30 BUILD_LIST 10
33 STORE_FAST 0 (l)
6 36 LOAD_GLOBAL 0 (sorted)
39 LOAD_FAST 0 (l)
42 CALL_FUNCTION 1
45 RETURN_VALUE
>>>
測試用例 3
更快的方式：
def a():
a, b, c, d, e, f, g, h, i, j = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
return j, i, h, g, f, e, d, c, b, a
>>>
>>> timeit(a, number=1000000)
... 0.216089963913
>>>
>>> dis(a)
5 0 LOAD_CONST 11 ((0, 1, 2, 3, 4, 5, 6, 7, 8, 9))
3 UNPACK_SEQUENCE 10
6 STORE_FAST 0 (a)
9 STORE_FAST 1 (b)
12 STORE_FAST 2 (c)
15 STORE_FAST 3 (d)
18 STORE_FAST 4 (e)
21 STORE_FAST 5 (f)
24 STORE_FAST 6 (g)
27 STORE_FAST 7 (h)
30 STORE_FAST 8 (i)
33 STORE_FAST 9 (j)
6 36 LOAD_FAST 9 (j)
39 LOAD_FAST 8 (i)
42 LOAD_FAST 7 (h)
45 LOAD_FAST 6 (g)
48 LOAD_FAST 5 (f)
51 LOAD_FAST 4 (e)
54 LOAD_FAST 3 (d)
57 LOAD_FAST 2 (c)
60 LOAD_FAST 1 (b)
63 LOAD_FAST 0 (a)
66 BUILD_TUPLE 10
69 RETURN_VALUE
>>>
更慢的方式：
def a():
a = 0
b = 1
c = 2
d = 3
e = 4
f = 5
g = 6
h = 7
i = 8
j = 9
return j, i, h, g, f, e, d, c, b, a
>>>
>>> timeit(a, number=1000000)
... 0.249029874802
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (0)
3 STORE_FAST 0 (a)
6 6 LOAD_CONST 2 (1)
9 STORE_FAST 1 (b)
7 12 LOAD_CONST 3 (2)
15 STORE_FAST 2 (c)
8 18 LOAD_CONST 4 (3)
21 STORE_FAST 3 (d)
9 24 LOAD_CONST 5 (4)
27 STORE_FAST 4 (e)
10 30 LOAD_CONST 6 (5)
33 STORE_FAST 5 (f)
11 36 LOAD_CONST 7 (6)
39 STORE_FAST 6 (g)
12 42 LOAD_CONST 8 (7)
45 STORE_FAST 7 (h)
13 48 LOAD_CONST 9 (8)
51 STORE_FAST 8 (i)
14 54 LOAD_CONST 10 (9)
57 STORE_FAST 9 (j)
15 60 LOAD_FAST 9 (j)
63 LOAD_FAST 8 (i)
66 LOAD_FAST 7 (h)
69 LOAD_FAST 6 (g)
72 LOAD_FAST 5 (f)
75 LOAD_FAST 4 (e)
78 LOAD_FAST 3 (d)
81 LOAD_FAST 2 (c)
84 LOAD_FAST 1 (b)
87 LOAD_FAST 0 (a)
90 BUILD_TUPLE 10
93 RETURN_VALUE
>>>
測試用例 4
更快的方式：
def a():
a, b, c, d, e, f = 2, 5, 52, 25, 225, 552
if a < b and b < c and c < d and d < e and e < f:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.176034927368
>>>
>>> dis(a)
5 0 LOAD_CONST 7 ((2, 5, 52, 25, 225, 552))
3 UNPACK_SEQUENCE 6
6 STORE_FAST 0 (a)
9 STORE_FAST 1 (b)
12 STORE_FAST 2 (c)
15 STORE_FAST 3 (d)
18 STORE_FAST 4 (e)
21 STORE_FAST 5 (f)
6 24 LOAD_FAST 0 (a)
27 LOAD_FAST 1 (b)
30 COMPARE_OP 0 (<)
33 POP_JUMP_IF_FALSE 88
36 LOAD_FAST 1 (b)
39 LOAD_FAST 2 (c)
42 COMPARE_OP 0 (<)
45 POP_JUMP_IF_FALSE 88
48 LOAD_FAST 2 (c)
51 LOAD_FAST 3 (d)
54 COMPARE_OP 0 (<)
57 POP_JUMP_IF_FALSE 88
60 LOAD_FAST 3 (d)
63 LOAD_FAST 4 (e)
66 COMPARE_OP 0 (<)
69 POP_JUMP_IF_FALSE 88
72 LOAD_FAST 4 (e)
75 LOAD_FAST 5 (f)
78 COMPARE_OP 0 (<)
81 POP_JUMP_IF_FALSE 88
7 84 LOAD_GLOBAL 0 (True)
87 RETURN_VALUE
8 >> 88 LOAD_GLOBAL 1 (False)
91 RETURN_VALUE
>>>
更慢的方式：
def a():
a, b, c, d, e, f = 2, 5, 52, 25, 225, 552
if a < b < c < d < e < f:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.208202123642
>>>
>>> dis(a)
5 0 LOAD_CONST 7 ((2, 5, 52, 25, 225, 552))
3 UNPACK_SEQUENCE 6
6 STORE_FAST 0 (a)
9 STORE_FAST 1 (b)
12 STORE_FAST 2 (c)
15 STORE_FAST 3 (d)
18 STORE_FAST 4 (e)
21 STORE_FAST 5 (f)
6 24 LOAD_FAST 0 (a)
27 LOAD_FAST 1 (b)
30 DUP_TOP
31 ROT_THREE
32 COMPARE_OP 0 (<)
35 JUMP_IF_FALSE_OR_POP 80
38 LOAD_FAST 2 (c)
41 DUP_TOP
42 ROT_THREE
43 COMPARE_OP 0 (<)
46 JUMP_IF_FALSE_OR_POP 80
49 LOAD_FAST 3 (d)
52 DUP_TOP
53 ROT_THREE
54 COMPARE_OP 0 (<)
57 JUMP_IF_FALSE_OR_POP 80
60 LOAD_FAST 4 (e)
63 DUP_TOP
64 ROT_THREE
65 COMPARE_OP 0 (<)
68 JUMP_IF_FALSE_OR_POP 80
71 LOAD_FAST 5 (f)
74 COMPARE_OP 0 (<)
77 JUMP_FORWARD 2 (to 82)
>> 80 ROT_TWO
81 POP_TOP
>> 82 POP_JUMP_IF_FALSE 89
7 85 LOAD_GLOBAL 0 (True)
88 RETURN_VALUE
8 >> 89 LOAD_GLOBAL 1 (False)
92 RETURN_VALUE
>>>
測試用例 5
更快的方式：
def a():
a = True
if a:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.109908103943
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (True)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 POP_JUMP_IF_FALSE 16
7 12 LOAD_GLOBAL 0 (True)
15 RETURN_VALUE
8 >> 16 LOAD_GLOBAL 1 (False)
19 RETURN_VALUE
>>>
更慢方式：
def a():
a = True
if a is True:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.141321897507
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (True)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 LOAD_GLOBAL 0 (True)
12 COMPARE_OP 8 (is)
15 POP_JUMP_IF_FALSE 22
7 18 LOAD_GLOBAL 0 (True)
21 RETURN_VALUE
8 >> 22 LOAD_GLOBAL 1 (False)
25 RETURN_VALUE
>>>
最慢的方式：
def a():
a = True
if a == True:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.149966001511
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (True)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 LOAD_GLOBAL 0 (True)
12 COMPARE_OP 2 (==)
15 POP_JUMP_IF_FALSE 22
7 18 LOAD_GLOBAL 0 (True)
21 RETURN_VALUE
8 >> 22 LOAD_GLOBAL 1 (False)
25 RETURN_VALUE
>>>
測試用例 6
更快的方式：
def a():
a = 1
if not a is 2:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.0980911254883
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 LOAD_CONST 2 (2)
12 COMPARE_OP 9 (is not)
15 POP_JUMP_IF_FALSE 22
7 18 LOAD_GLOBAL 0 (True)
21 RETURN_VALUE
8 >> 22 LOAD_GLOBAL 1 (False)
25 RETURN_VALUE
>>>
更慢的方式：
def a():
a = 1
if a is not 2:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.10059595108
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 LOAD_CONST 2 (2)
12 COMPARE_OP 9 (is not)
15 POP_JUMP_IF_FALSE 22
7 18 LOAD_GLOBAL 0 (True)
21 RETURN_VALUE
8 >> 22 LOAD_GLOBAL 1 (False)
25 RETURN_VALUE
>>>
最慢的方式：
def a():
a = 1
if a != 2:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.102056026459
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 LOAD_CONST 2 (2)
12 COMPARE_OP 3 (!=)
15 POP_JUMP_IF_FALSE 22
7 18 LOAD_GLOBAL 0 (True)
21 RETURN_VALUE
8 >> 22 LOAD_GLOBAL 1 (False)
25 RETURN_VALUE
>>>
測試用例 7
更快的方式：
def a():
a = []
if a:
return False
return True
>>>
>>> timeit(a, number=1000000)
... 0.111177921295
>>>
>>> dis(a)
5 0 BUILD_LIST 0
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 POP_JUMP_IF_FALSE 16
7 12 LOAD_GLOBAL 0 (False)
15 RETURN_VALUE
8 >> 16 LOAD_GLOBAL 1 (True)
19 RETURN_VALUE
>>>
更慢的方式：
def a():
a = []
if not a:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.113872051239
>>>
>>> dis(a)
5 0 BUILD_LIST 0
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 POP_JUMP_IF_TRUE 16
7 12 LOAD_GLOBAL 0 (True)
15 RETURN_VALUE
8 >> 16 LOAD_GLOBAL 1 (False)
19 RETURN_VALUE
>>>
最慢的方式：
def a():
a = []
if len(a) >>
>>> timeit(a, number=1000000)
... 0.13893699646
>>>
>>> dis(a)
5 0 BUILD_LIST 0
3 STORE_FAST 0 (a)
6 6 LOAD_GLOBAL 0 (len)
9 LOAD_FAST 0 (a)
12 CALL_FUNCTION 1
15 LOAD_CONST 1 (0)
18 COMPARE_OP 1 (> 28 LOAD_GLOBAL 2 (False)
31 RETURN_VALUE
>>>
超級慢的方式：
def a():
a = []
if a == []:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.16094994545
>>>
>>> dis(a)
5 0 BUILD_LIST 0
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 BUILD_LIST 0
12 COMPARE_OP 2 (==)
15 POP_JUMP_IF_FALSE 22
7 18 LOAD_GLOBAL 0 (True)
21 RETURN_VALUE
8 >> 22 LOAD_GLOBAL 1 (False)
25 RETURN_VALUE
>>>
測試用例 8
更快的方式：
def a():
a = object()
if not a:
return False
return True
>>>
>>> timeit(a, number=1000000)
... 0.150635004044
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (object)
3 CALL_FUNCTION 0
6 STORE_FAST 0 (a)
6 9 LOAD_FAST 0 (a)
12 POP_JUMP_IF_TRUE 19
7 15 LOAD_GLOBAL 1 (False)
18 RETURN_VALUE
8 >> 19 LOAD_GLOBAL 2 (True)
22 RETURN_VALUE
>>>
更慢的方式：
def a():
a = object()
if a is None:
return False
return True
>>>
>>> timeit(a, number=1000000)
... 0.15754199028
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (object)
3 CALL_FUNCTION 0
6 STORE_FAST 0 (a)
6 9 LOAD_FAST 0 (a)
12 LOAD_CONST 0 (None)
15 COMPARE_OP 8 (is)
18 POP_JUMP_IF_FALSE 25
7 21 LOAD_GLOBAL 2 (False)
24 RETURN_VALUE
8 >> 25 LOAD_GLOBAL 3 (True)
28 RETURN_VALUE
>>>
最慢的方式：
def a():
a = object()
if a:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.157824993134
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (object)
3 CALL_FUNCTION 0
6 STORE_FAST 0 (a)
6 9 LOAD_FAST 0 (a)
12 POP_JUMP_IF_FALSE 19
7 15 LOAD_GLOBAL 1 (True)
18 RETURN_VALUE
8 >> 19 LOAD_GLOBAL 2 (False)
22 RETURN_VALUE
>>>
超級慢的方式：
def a():
a = object()
if a is not None:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.181853055954
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (object)
3 CALL_FUNCTION 0
6 STORE_FAST 0 (a)
6 9 LOAD_FAST 0 (a)
12 LOAD_CONST 0 (None)
15 COMPARE_OP 9 (is not)
18 POP_JUMP_IF_FALSE 25
7 21 LOAD_GLOBAL 2 (True)
24 RETURN_VALUE
8 >> 25 LOAD_GLOBAL 3 (False)
28 RETURN_VALUE
>>>
測試用例 9
更快的方式：
def a():
a = [1, 2, 3, 4, 5]
s = 0
for p, v in enumerate(a):
s += p
s += v
return s
>>>
>>> timeit(a, number=1000000)
... 0.738418102264
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 LOAD_CONST 4 (4)
12 LOAD_CONST 5 (5)
15 BUILD_LIST 5
18 STORE_FAST 0 (a)
6 21 LOAD_CONST 6 (0)
24 STORE_FAST 1 (s)
7 27 SETUP_LOOP 46 (to 76)
30 LOAD_GLOBAL 0 (enumerate)
33 LOAD_FAST 0 (a)
36 CALL_FUNCTION 1
39 GET_ITER
>> 40 FOR_ITER 32 (to 75)
43 UNPACK_SEQUENCE 2
46 STORE_FAST 2 (p)
49 STORE_FAST 3 (v)
8 52 LOAD_FAST 1 (s)
55 LOAD_FAST 2 (p)
58 INPLACE_ADD
59 STORE_FAST 1 (s)
9 62 LOAD_FAST 1 (s)
65 LOAD_FAST 3 (v)
68 INPLACE_ADD
69 STORE_FAST 1 (s)
72 JUMP_ABSOLUTE 40
>> 75 POP_BLOCK
10 >> 76 LOAD_FAST 1 (s)
79 RETURN_VALUE
>>>
更慢的方式：
def a():
a = [1, 2, 3, 4, 5]
s = 0
for i in range(len(a)):
s += i
s += a[i]
return s
>>>
>>> timeit(a, number=1000000)
... 0.800552845001
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 LOAD_CONST 4 (4)
12 LOAD_CONST 5 (5)
15 BUILD_LIST 5
18 STORE_FAST 0 (a)
6 21 LOAD_CONST 6 (0)
24 STORE_FAST 1 (s)
7 27 SETUP_LOOP 50 (to 80)
30 LOAD_GLOBAL 0 (range)
33 LOAD_GLOBAL 1 (len)
36 LOAD_FAST 0 (a)
39 CALL_FUNCTION 1
42 CALL_FUNCTION 1
45 GET_ITER
>> 46 FOR_ITER 30 (to 79)
49 STORE_FAST 2 (i)
8 52 LOAD_FAST 1 (s)
55 LOAD_FAST 2 (i)
58 INPLACE_ADD
59 STORE_FAST 1 (s)
9 62 LOAD_FAST 1 (s)
65 LOAD_FAST 0 (a)
68 LOAD_FAST 2 (i)
71 BINARY_SUBSCR
72 INPLACE_ADD
73 STORE_FAST 1 (s)
76 JUMP_ABSOLUTE 46
>> 79 POP_BLOCK
10 >> 80 LOAD_FAST 1 (s)
83 RETURN_VALUE
>>>
測試用例 10
更快的方式：
def a():
r = ''
for i in range(10):
r += str(i)
return r
>>>
>>> timeit(a, number=1000000)
... 1.63575387001
>>>
>>> dis(a)
5 0 LOAD_CONST 1 ('')
3 STORE_FAST 0 (r)
6 6 SETUP_LOOP 36 (to 45)
9 LOAD_GLOBAL 0 (range)
12 LOAD_CONST 2 (10)
15 CALL_FUNCTION 1
18 GET_ITER
>> 19 FOR_ITER 22 (to 44)
22 STORE_FAST 1 (i)
7 25 LOAD_FAST 0 (r)
28 LOAD_GLOBAL 1 (str)
31 LOAD_FAST 1 (i)
34 CALL_FUNCTION 1
37 INPLACE_ADD
38 STORE_FAST 0 (r)
41 JUMP_ABSOLUTE 19
>> 44 POP_BLOCK
8 >> 45 LOAD_FAST 0 (r)
48 RETURN_VALUE
>>>
更慢的方式：
def a():
r = []
for i in range(10):
r.append(str(i))
return ''.join(r)
>>>
>>> timeit(a, number=1000000)
... 2.1280169487
>>>
>>> dis(a)
5 0 BUILD_LIST 0
3 STORE_FAST 0 (r)
6 6 SETUP_LOOP 39 (to 48)
9 LOAD_GLOBAL 0 (range)
12 LOAD_CONST 1 (10)
15 CALL_FUNCTION 1
18 GET_ITER
>> 19 FOR_ITER 25 (to 47)
22 STORE_FAST 1 (i)
7 25 LOAD_FAST 0 (r)
28 LOAD_ATTR 1 (append)
31 LOAD_GLOBAL 2 (str)
34 LOAD_FAST 1 (i)
37 CALL_FUNCTION 1
40 CALL_FUNCTION 1
43 POP_TOP
44 JUMP_ABSOLUTE 19
>> 47 POP_BLOCK
8 >> 48 LOAD_CONST 2 ('')
51 LOAD_ATTR 3 (join)
54 LOAD_FAST 0 (r)
57 CALL_FUNCTION 1
60 RETURN_VALUE
>>>
測試用例 11
更快的方式：
def a():
a = 5
b = 2
c = 3
return "%s" % (a*(b+c))
>>>
>>> timeit(a, number=1000000)
... 0.229720830917
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (5)
3 STORE_FAST 0 (a)
6 6 LOAD_CONST 2 (2)
9 STORE_FAST 1 (b)
7 12 LOAD_CONST 3 (3)
15 STORE_FAST 2 (c)
8 18 LOAD_CONST 4 ('%s')
21 LOAD_FAST 0 (a)
24 LOAD_FAST 1 (b)
27 LOAD_FAST 2 (c)
30 BINARY_ADD
31 BINARY_MULTIPLY
32 BINARY_MODULO
33 RETURN_VALUE
>>>
更慢的方式：
def a():
a = 5
b = 2
c = 3
return str(a*(b+c))
>>>
>>> timeit(a, number=1000000)
... 0.25043797493
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (5)
3 STORE_FAST 0 (a)
6 6 LOAD_CONST 2 (2)
9 STORE_FAST 1 (b)
7 12 LOAD_CONST 3 (3)
15 STORE_FAST 2 (c)
8 18 LOAD_GLOBAL 0 (str)
21 LOAD_FAST 0 (a)
24 LOAD_FAST 1 (b)
27 LOAD_FAST 2 (c)
30 BINARY_ADD
31 BINARY_MULTIPLY
32 CALL_FUNCTION 1
35 RETURN_VALUE
>>>
最慢的方式：
def a():
a = 5
b = 2
c = 3
return "%d" % (a*(b+c))
>>>
>>> timeit(a, number=1000000)
... 0.583065986633
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (5)
3 STORE_FAST 0 (a)
6 6 LOAD_CONST 2 (2)
9 STORE_FAST 1 (b)
7 12 LOAD_CONST 3 (3)
15 STORE_FAST 2 (c)
8 18 LOAD_CONST 4 ('%d')
21 LOAD_FAST 0 (a)
24 LOAD_FAST 1 (b)
27 LOAD_FAST 2 (c)
30 BINARY_ADD
31 BINARY_MULTIPLY
32 BINARY_MODULO
33 RETURN_VALUE
>>>
測試用例 12
更快的方式：
def a():
a = [1, 2, 3, 4, 5]
return len(a)
>>>
>>> timeit(a, number=1000000)
... 0.194615840912
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 LOAD_CONST 4 (4)
12 LOAD_CONST 5 (5)
15 BUILD_LIST 5
18 STORE_FAST 0 (a)
6 21 LOAD_GLOBAL 0 (len)
24 LOAD_FAST 0 (a)
27 CALL_FUNCTION 1
30 RETURN_VALUE
>>>
更慢的方式：
def a():
a = [1, 2, 3, 4, 5]
return a.__len__()
>>>
>>> timeit(a, number=1000000)
... 0.220345020294
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 LOAD_CONST 4 (4)
12 LOAD_CONST 5 (5)
15 BUILD_LIST 5
18 STORE_FAST 0 (a)
6 21 LOAD_FAST 0 (a)
24 LOAD_ATTR 0 (__len__)
27 CALL_FUNCTION 0
30 RETURN_VALUE
>>>
測試用例 13
更快的方式：
def a():
a = 1
b = 2
c = 2
d = 5
return (a+b+c)*d
>>>
>>> timeit(a, number=1000000)
... 0.170273065567
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 STORE_FAST 0 (a)
6 6 LOAD_CONST 2 (2)
9 STORE_FAST 1 (b)
7 12 LOAD_CONST 2 (2)
15 STORE_FAST 2 (c)
8 18 LOAD_CONST 3 (5)
21 STORE_FAST 3 (d)
9 24 LOAD_FAST 0 (a)
27 LOAD_FAST 1 (b)
30 BINARY_ADD
31 LOAD_FAST 2 (c)
34 BINARY_ADD
35 LOAD_FAST 3 (d)
38 BINARY_MULTIPLY
39 RETURN_VALUE
>>>
更慢的方式：
def a():
a = 1
b = 2
c = 2
d = 5
return (a.__add__(b.__add__(c))).__mul__(d)
>>>
>>> timeit(a, number=1000000)
... 0.363096952438
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 STORE_FAST 0 (a)
6 6 LOAD_CONST 2 (2)
9 STORE_FAST 1 (b)
7 12 LOAD_CONST 2 (2)
15 STORE_FAST 2 (c)
8 18 LOAD_CONST 3 (5)
21 STORE_FAST 3 (d)
9 24 LOAD_FAST 0 (a)
27 LOAD_ATTR 0 (__add__)
30 LOAD_FAST 1 (b)
33 LOAD_ATTR 0 (__add__)
36 LOAD_FAST 2 (c)
39 CALL_FUNCTION 1
42 CALL_FUNCTION 1
45 LOAD_ATTR 1 (__mul__)
48 LOAD_FAST 3 (d)
51 CALL_FUNCTION 1
54 RETURN_VALUE
>>>
測試用例 14
更快的方式：
class Z():
def__init__(self, v):
self.v = v
def__mul__(self, o):
return Z(self.v * o.v)
def__add__(self, o):
return Z(self.v + o.v)
def a():
a = Z(5)
b = Z(2)
c = Z(3)
return (b.__add__(c)).__mul__(a)
>>>
>>> timeit(a, number=1000000)
... 1.7775759697
>>>
>>> dis(a)
17 0 LOAD_GLOBAL 0 (Z)
3 LOAD_CONST 1 (5)
6 CALL_FUNCTION 1
9 STORE_FAST 0 (a)
18 12 LOAD_GLOBAL 0 (Z)
15 LOAD_CONST 2 (2)
18 CALL_FUNCTION 1
21 STORE_FAST 1 (b)
19 24 LOAD_GLOBAL 0 (Z)
27 LOAD_CONST 3 (3)
30 CALL_FUNCTION 1
33 STORE_FAST 2 (c)
20 36 LOAD_FAST 1 (b)
39 LOAD_ATTR 1 (__add__)
42 LOAD_FAST 2 (c)
45 CALL_FUNCTION 1
48 LOAD_ATTR 2 (__mul__)
51 LOAD_FAST 0 (a)
54 CALL_FUNCTION 1
57 RETURN_VALUE
>>>
更慢的方式：
class Z():
def__init__(self, v):
self.v = v
def__mul__(self, o):
return Z(self.v * o.v)
def__add__(self, o):
return Z(self.v + o.v)
def a():
a = Z(5)
b = Z(2)
c = Z(3)
return (b + c) * a
>>>
>>> timeit(a, number=1000000)
... 2.79053497314
>>>
>>> dis(a)
17 0 LOAD_GLOBAL 0 (Z)
3 LOAD_CONST 1 (5)
6 CALL_FUNCTION 1
9 STORE_FAST 0 (a)
18 12 LOAD_GLOBAL 0 (Z)
15 LOAD_CONST 2 (2)
18 CALL_FUNCTION 1
21 STORE_FAST 1 (b)
19 24 LOAD_GLOBAL 0 (Z)
27 LOAD_CONST 3 (3)
30 CALL_FUNCTION 1
33 STORE_FAST 2 (c)
20 36 LOAD_FAST 1 (b)
39 LOAD_FAST 2 (c)
42 BINARY_ADD
43 LOAD_FAST 0 (a)
46 BINARY_MULTIPLY
47 RETURN_VALUE
>>>
測試用例 15
更快的方式：
def a():
s = 0
for i in range(50000):
s += i
return s
number = 100000
>>>
>>> timeit(a, number=100000)
... 177.31340313
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (0)
3 STORE_FAST 0 (s)
6 6 SETUP_LOOP 30 (to 39)
9 LOAD_GLOBAL 0 (range)
12 LOAD_CONST 2 (50000)
15 CALL_FUNCTION 1
18 GET_ITER
>> 19 FOR_ITER 16 (to 38)
22 STORE_FAST 1 (i)
7 25 LOAD_FAST 0 (s)
28 LOAD_FAST 1 (i)
31 INPLACE_ADD
32 STORE_FAST 0 (s)
35 JUMP_ABSOLUTE 19
>> 38 POP_BLOCK
8 >> 39 LOAD_FAST 0 (s)
42 RETURN_VALUE
>>>
更慢的方式：
def a():
return sum(i for i in range(50000))
number = 100000
>>>
>>> timeit(a, number=100000)
... 215.36849308
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (sum)
3 LOAD_CONST 1 (<code> at 0x7f7357e854b0, file "/tmp/__pfw_test15_t2.py", line 5>)
6 MAKE_FUNCTION 0
9 LOAD_GLOBAL 1 (range)
12 LOAD_CONST 2 (50000)
15 CALL_FUNCTION 1
18 GET_ITER
19 CALL_FUNCTION 1
22 CALL_FUNCTION 1
25 RETURN_VALUE
>>>
</code>
測試用例 16
更快的方式：
def a():
return [i for i in range(1000)]
number = 100000
>>>
>>> timeit(a, number=100000)
... 3.07614183426
>>>
>>> dis(a)
5 0 BUILD_LIST 0
3 LOAD_GLOBAL 0 (range)
6 LOAD_CONST 1 (1000)
9 CALL_FUNCTION 1
12 GET_ITER
>> 13 FOR_ITER 12 (to 28)
16 STORE_FAST 0 (i)
19 LOAD_FAST 0 (i)
22 LIST_APPEND 2
25 JUMP_ABSOLUTE 13
>> 28 RETURN_VALUE
>>>
更慢的方式：
def a():
l = []
for i in range(1000):
l.append(i)
return l
number = 100000
>>>
>>> timeit(a, number=100000)
... 6.29185986519
>>>
>>> dis(a)
5 0 BUILD_LIST 0
3 STORE_FAST 0 (l)
6 6 SETUP_LOOP 33 (to 42)
9 LOAD_GLOBAL 0 (range)
12 LOAD_CONST 1 (1000)
15 CALL_FUNCTION 1
18 GET_ITER
>> 19 FOR_ITER 19 (to 41)
22 STORE_FAST 1 (i)
7 25 LOAD_FAST 0 (l)
28 LOAD_ATTR 1 (append)
31 LOAD_FAST 1 (i)
34 CALL_FUNCTION 1
37 POP_TOP
38 JUMP_ABSOLUTE 19
>> 41 POP_BLOCK
8 >> 42 LOAD_FAST 0 (l)
45 RETURN_VALUE
>>>
測試用例 17
更快的方式：
def a():
return {str(i): i*2 for i in range(100)}
>>>
>>> timeit(a, number=1000000)
... 17.8982248306
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (<code> at 0x7f81ea7854b0, file "/tmp/__pfw_test17_t3.py", line 5>)
3 MAKE_FUNCTION 0
6 LOAD_GLOBAL 0 (range)
9 LOAD_CONST 2 (100)
12 CALL_FUNCTION 1
15 GET_ITER
16 CALL_FUNCTION 1
19 RETURN_VALUE
>>>
</code>
更慢的方式：
def a():
d = {}
for i in range(100):
d[str(i)] = i*2
return d
>>>
>>> timeit(a, number=1000000)
... 18.513548851
>>>
>>> dis(a)
5 0 BUILD_MAP 0
3 STORE_FAST 0 (d)
6 6 SETUP_LOOP 40 (to 49)
9 LOAD_GLOBAL 0 (range)
12 LOAD_CONST 1 (100)
15 CALL_FUNCTION 1
18 GET_ITER
>> 19 FOR_ITER 26 (to 48)
22 STORE_FAST 1 (i)
7 25 LOAD_FAST 1 (i)
28 LOAD_CONST 2 (2)
31 BINARY_MULTIPLY
32 LOAD_FAST 0 (d)
35 LOAD_GLOBAL 1 (str)
38 LOAD_FAST 1 (i)
41 CALL_FUNCTION 1
44 STORE_SUBSCR
45 JUMP_ABSOLUTE 19
>> 48 POP_BLOCK
8 >> 49 LOAD_FAST 0 (d)
52 RETURN_VALUE
>>>
最慢的方式：
def a():
d = {}
for i in range(100):
d.update({str(i): i*2})
return d
>>>
>>> timeit(a, number=1000000)
... 36.9908900261
>>>
>>> dis(a)
5 0 BUILD_MAP 0
3 STORE_FAST 0 (d)
6 6 SETUP_LOOP 50 (to 59)
9 LOAD_GLOBAL 0 (range)
12 LOAD_CONST 1 (100)
15 CALL_FUNCTION 1
18 GET_ITER
>> 19 FOR_ITER 36 (to 58)
22 STORE_FAST 1 (i)
7 25 LOAD_FAST 0 (d)
28 LOAD_ATTR 1 (update)
31 BUILD_MAP 1
34 LOAD_FAST 1 (i)
37 LOAD_CONST 2 (2)
40 BINARY_MULTIPLY
41 LOAD_GLOBAL 2 (str)
44 LOAD_FAST 1 (i)
47 CALL_FUNCTION 1
50 STORE_MAP
51 CALL_FUNCTION 1
54 POP_TOP
55 JUMP_ABSOLUTE 19
>> 58 POP_BLOCK
8 >> 59 LOAD_FAST 0 (d)
62 RETURN_VALUE
>>>
測試用例 18
更快的方式：
def a():
l = range(50, -20, -2)
return {p: v for p, v in enumerate(l)}
>>>
>>> timeit(a, number=1000000)
... 2.82184195518
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (range)
3 LOAD_CONST 1 (50)
6 LOAD_CONST 2 (-20)
9 LOAD_CONST 3 (-2)
12 CALL_FUNCTION 3
15 STORE_FAST 0 (l)
6 18 LOAD_CONST 4 (<code> at 0x7ff850f7a4b0, file "/tmp/__pfw_test18_t3.py", line 6>)
21 MAKE_FUNCTION 0
24 LOAD_GLOBAL 1 (enumerate)
27 LOAD_FAST 0 (l)
30 CALL_FUNCTION 1
33 GET_ITER
34 CALL_FUNCTION 1
37 RETURN_VALUE
>>>
</code>
更慢的方式：
def a():
l = range(50, -20, -2)
d = {}
for p, v in enumerate(l):
d[p] = v
return d
>>>
>>> timeit(a, number=1000000)
... 3.04933786392
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (range)
3 LOAD_CONST 1 (50)
6 LOAD_CONST 2 (-20)
9 LOAD_CONST 3 (-2)
12 CALL_FUNCTION 3
15 STORE_FAST 0 (l)
6 18 BUILD_MAP 0
21 STORE_FAST 1 (d)
7 24 SETUP_LOOP 36 (to 63)
27 LOAD_GLOBAL 1 (enumerate)
30 LOAD_FAST 0 (l)
33 CALL_FUNCTION 1
36 GET_ITER
>> 37 FOR_ITER 22 (to 62)
40 UNPACK_SEQUENCE 2
43 STORE_FAST 2 (p)
46 STORE_FAST 3 (v)
8 49 LOAD_FAST 3 (v)
52 LOAD_FAST 1 (d)
55 LOAD_FAST 2 (p)
58 STORE_SUBSCR
59 JUMP_ABSOLUTE 37
>> 62 POP_BLOCK
9 >> 63 LOAD_FAST 1 (d)
66 RETURN_VALUE
>>>
最慢的方式：
def a():
l = range(50, -20, -2)
d = {}
for p, v in enumerate(l):
d.update({p: v})
return d
>>>
>>> timeit(a, number=1000000)
... 9.87823104858
>>>
>>> dis(a)
5 0 LOAD_GLOBAL 0 (range)
3 LOAD_CONST 1 (50)
6 LOAD_CONST 2 (-20)
9 LOAD_CONST 3 (-2)
12 CALL_FUNCTION 3
15 STORE_FAST 0 (l)
6 18 BUILD_MAP 0
21 STORE_FAST 1 (d)
7 24 SETUP_LOOP 46 (to 73)
27 LOAD_GLOBAL 1 (enumerate)
30 LOAD_FAST 0 (l)
33 CALL_FUNCTION 1
36 GET_ITER
>> 37 FOR_ITER 32 (to 72)
40 UNPACK_SEQUENCE 2
43 STORE_FAST 2 (p)
46 STORE_FAST 3 (v)
8 49 LOAD_FAST 1 (d)
52 LOAD_ATTR 2 (update)
55 BUILD_MAP 1
58 LOAD_FAST 3 (v)
61 LOAD_FAST 2 (p)
64 STORE_MAP
65 CALL_FUNCTION 1
68 POP_TOP
69 JUMP_ABSOLUTE 37
>> 72 POP_BLOCK
9 >> 73 LOAD_FAST 1 (d)
76 RETURN_VALUE
>>>
測試用例 19
更快的方式：
def a():
a = 1
if a == 1 or a == 2 or a == 3:
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.100009918213
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 LOAD_CONST 1 (1)
12 COMPARE_OP 2 (==)
15 POP_JUMP_IF_TRUE 42
18 LOAD_FAST 0 (a)
21 LOAD_CONST 2 (2)
24 COMPARE_OP 2 (==)
27 POP_JUMP_IF_TRUE 42
30 LOAD_FAST 0 (a)
33 LOAD_CONST 3 (3)
36 COMPARE_OP 2 (==)
39 POP_JUMP_IF_FALSE 46
7 >> 42 LOAD_GLOBAL 0 (True)
45 RETURN_VALUE
8 >> 46 LOAD_GLOBAL 1 (False)
49 RETURN_VALUE
>>>
更慢的方式：
def a():
a = 1
if a in (1, 2, 3):
return True
return False
>>>
>>> timeit(a, number=1000000)
... 0.105048894882
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 STORE_FAST 0 (a)
6 6 LOAD_FAST 0 (a)
9 LOAD_CONST 4 ((1, 2, 3))
12 COMPARE_OP 6 (in)
15 POP_JUMP_IF_FALSE 22
7 18 LOAD_GLOBAL 0 (True)
21 RETURN_VALUE
8 >> 22 LOAD_GLOBAL 1 (False)
25 RETURN_VALUE
>>>
測試用例 20
更快的方式：
<code>
<br/>
</code>
更慢的方式：
<code>
<br/>
</code>
最慢的方式：
<code>
<br/>
</code>
測試用例 21
更快的方式：
def a():
return ''.join(map(str, xrange(10)))
>>>
>>> timeit(a, number=1000000)
... 1.28661704063
>>>
>>> dis(a)
5 0 LOAD_CONST 1 ('')
3 LOAD_ATTR 0 (join)
6 LOAD_GLOBAL 1 (map)
9 LOAD_GLOBAL 2 (str)
12 LOAD_GLOBAL 3 (xrange)
15 LOAD_CONST 2 (10)
18 CALL_FUNCTION 1
21 CALL_FUNCTION 2
24 CALL_FUNCTION 1
27 RETURN_VALUE
>>>
更慢的方式：
def a():
return ''.join(map(str, range(10)))
>>>
>>> timeit(a, number=1000000)
... 1.29610896111
>>>
>>> dis(a)
5 0 LOAD_CONST 1 ('')
3 LOAD_ATTR 0 (join)
6 LOAD_GLOBAL 1 (map)
9 LOAD_GLOBAL 2 (str)
12 LOAD_GLOBAL 3 (range)
15 LOAD_CONST 2 (10)
18 CALL_FUNCTION 1
21 CALL_FUNCTION 2
24 CALL_FUNCTION 1
27 RETURN_VALUE
>>>
最慢的方式：
def a():
r = ''
for i in range(10):
r = '%s%s' % (r, str(i))
return r
>>>
>>> timeit(a, number=1000000)
... 2.74961709976
>>>
>>> dis(a)
5 0 LOAD_CONST 1 ('')
3 STORE_FAST 0 (r)
6 6 SETUP_LOOP 42 (to 51)
9 LOAD_GLOBAL 0 (range)
12 LOAD_CONST 2 (10)
15 CALL_FUNCTION 1
18 GET_ITER
>> 19 FOR_ITER 28 (to 50)
22 STORE_FAST 1 (i)
7 25 LOAD_CONST 3 ('%s%s')
28 LOAD_FAST 0 (r)
31 LOAD_GLOBAL 1 (str)
34 LOAD_FAST 1 (i)
37 CALL_FUNCTION 1
40 BUILD_TUPLE 2
43 BINARY_MODULO
44 STORE_FAST 0 (r)
47 JUMP_ABSOLUTE 19
>> 50 POP_BLOCK
8 >> 51 LOAD_FAST 0 (r)
54 RETURN_VALUE
>>>
測試用例 22
更快的方式：
def a(n=25):
a, b = 0, 1
for i in range(n):
x = a + b
a = b
b = x
return a
>>>
>>> timeit(a, number=1000000)
... 1.34775996208
>>>
>>> dis(a)
5 0 LOAD_CONST 3 ((0, 1))
3 UNPACK_SEQUENCE 2
6 STORE_FAST 1 (a)
9 STORE_FAST 2 (b)
6 12 SETUP_LOOP 42 (to 57)
15 LOAD_GLOBAL 0 (range)
18 LOAD_FAST 0 (n)
21 CALL_FUNCTION 1
24 GET_ITER
>> 25 FOR_ITER 28 (to 56)
28 STORE_FAST 3 (i)
7 31 LOAD_FAST 1 (a)
34 LOAD_FAST 2 (b)
37 BINARY_ADD
38 STORE_FAST 4 (x)
8 41 LOAD_FAST 2 (b)
44 STORE_FAST 1 (a)
9 47 LOAD_FAST 4 (x)
50 STORE_FAST 2 (b)
53 JUMP_ABSOLUTE 25
>> 56 POP_BLOCK
10 >> 57 LOAD_FAST 1 (a)
60 RETURN_VALUE
>>>
更慢的方式：
def a(n=25):
a, b = 0, 1
for i in range(n):
a, b = b, a + b
return a
>>>
>>> timeit(a, number=1000000)
... 1.46058106422
>>>
>>> dis(a)
5 0 LOAD_CONST 3 ((0, 1))
3 UNPACK_SEQUENCE 2
6 STORE_FAST 1 (a)
9 STORE_FAST 2 (b)
6 12 SETUP_LOOP 37 (to 52)
15 LOAD_GLOBAL 0 (range)
18 LOAD_FAST 0 (n)
21 CALL_FUNCTION 1
24 GET_ITER
>> 25 FOR_ITER 23 (to 51)
28 STORE_FAST 3 (i)
7 31 LOAD_FAST 2 (b)
34 LOAD_FAST 1 (a)
37 LOAD_FAST 2 (b)
40 BINARY_ADD
41 ROT_TWO
42 STORE_FAST 1 (a)
45 STORE_FAST 2 (b)
48 JUMP_ABSOLUTE 25
>> 51 POP_BLOCK
8 >> 52 LOAD_FAST 1 (a)
55 RETURN_VALUE
>>>
測試用例 23
更快的方式：
def a():
x, y, z, w, k = 0, 0, 0, 0, 0
return x, y, z, w, k
>>>
>>> timeit(a, number=1000000)
... 0.168544054031
>>>
>>> dis(a)
5 0 LOAD_CONST 2 ((0, 0, 0, 0, 0))
3 UNPACK_SEQUENCE 5
6 STORE_FAST 0 (x)
9 STORE_FAST 1 (y)
12 STORE_FAST 2 (z)
15 STORE_FAST 3 (w)
18 STORE_FAST 4 (k)
6 21 LOAD_FAST 0 (x)
24 LOAD_FAST 1 (y)
27 LOAD_FAST 2 (z)
30 LOAD_FAST 3 (w)
33 LOAD_FAST 4 (k)
36 BUILD_TUPLE 5
39 RETURN_VALUE
>>>
更慢的方式：
def a():
x = 0
y = 0
z = 0
w = 0
k = 0
return x, y, z, w, k
>>>
>>> timeit(a, number=1000000)
... 0.174968957901
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (0)
3 STORE_FAST 0 (x)
6 6 LOAD_CONST 1 (0)
9 STORE_FAST 1 (y)
7 12 LOAD_CONST 1 (0)
15 STORE_FAST 2 (z)
8 18 LOAD_CONST 1 (0)
21 STORE_FAST 3 (w)
9 24 LOAD_CONST 1 (0)
27 STORE_FAST 4 (k)
10 30 LOAD_FAST 0 (x)
33 LOAD_FAST 1 (y)
36 LOAD_FAST 2 (z)
39 LOAD_FAST 3 (w)
42 LOAD_FAST 4 (k)
45 BUILD_TUPLE 5
48 RETURN_VALUE
>>>
最慢的方式：
def a():
x = y = z = w = k = 0
return x, y, z, w, k
>>>
>>> timeit(a, number=1000000)
... 0.205312013626
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (0)
3 DUP_TOP
4 STORE_FAST 0 (x)
7 DUP_TOP
8 STORE_FAST 1 (y)
11 DUP_TOP
12 STORE_FAST 2 (z)
15 DUP_TOP
16 STORE_FAST 3 (w)
19 STORE_FAST 4 (k)
6 22 LOAD_FAST 0 (x)
25 LOAD_FAST 1 (y)
28 LOAD_FAST 2 (z)
31 LOAD_FAST 3 (w)
34 LOAD_FAST 4 (k)
37 BUILD_TUPLE 5
40 RETURN_VALUE
>>>
測試用例 24
更快的方式：
def a():
a = [[1, 2, 3], [2, 3, 4], [4, 5, 6]]
b = {k: v for x, k, v in a}
return b
>>>
>>> timeit(a, number=1000000)
... 0.717478990555
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 BUILD_LIST 3
12 LOAD_CONST 2 (2)
15 LOAD_CONST 3 (3)
18 LOAD_CONST 4 (4)
21 BUILD_LIST 3
24 LOAD_CONST 4 (4)
27 LOAD_CONST 5 (5)
30 LOAD_CONST 6 (6)
33 BUILD_LIST 3
36 BUILD_LIST 3
39 STORE_FAST 0 (a)
6 42 LOAD_CONST 7 (<code> at 0x7f9e6e6b94b0, file "/tmp/__pfw_test24_t3.py", line 6>)
45 MAKE_FUNCTION 0
48 LOAD_FAST 0 (a)
51 GET_ITER
52 CALL_FUNCTION 1
55 STORE_FAST 1 (b)
7 58 LOAD_FAST 1 (b)
61 RETURN_VALUE
>>>
</code>
更慢的方式：
def a():
a = [[1, 2, 3], [2, 3, 4], [4, 5, 6]]
b = {x[1]: x[2] for x in a}
return b
>>>
>>> timeit(a, number=1000000)
... 0.744184017181
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 BUILD_LIST 3
12 LOAD_CONST 2 (2)
15 LOAD_CONST 3 (3)
18 LOAD_CONST 4 (4)
21 BUILD_LIST 3
24 LOAD_CONST 4 (4)
27 LOAD_CONST 5 (5)
30 LOAD_CONST 6 (6)
33 BUILD_LIST 3
36 BUILD_LIST 3
39 STORE_FAST 0 (a)
6 42 LOAD_CONST 7 (<code> at 0x7fcc514754b0, file "/tmp/__pfw_test24_t1.py", line 6>)
45 MAKE_FUNCTION 0
48 LOAD_FAST 0 (a)
51 GET_ITER
52 CALL_FUNCTION 1
55 STORE_FAST 1 (b)
7 58 LOAD_FAST 1 (b)
61 RETURN_VALUE
>>>
</code>
最慢的方式：
def a():
a = [[1, 2, 3], [2, 3, 4], [4, 5, 6]]
b = dict((x, y)for w, x, y in a)
return b
>>>
>>> timeit(a, number=1000000)
... 1.32197403908
>>>
>>> dis(a)
5 0 LOAD_CONST 1 (1)
3 LOAD_CONST 2 (2)
6 LOAD_CONST 3 (3)
9 BUILD_LIST 3
12 LOAD_CONST 2 (2)
15 LOAD_CONST 3 (3)
18 LOAD_CONST 4 (4)
21 BUILD_LIST 3
24 LOAD_CONST 4 (4)
27 LOAD_CONST 5 (5)
30 LOAD_CONST 6 (6)
33 BUILD_LIST 3
36 BUILD_LIST 3
39 STORE_FAST 0 (a)
6 42 LOAD_GLOBAL 0 (dict)
45 LOAD_CONST 7 (<code> at 0x7f5ea06174b0, file "/tmp/__pfw_test24_t2.py", line 6>)
48 MAKE_FUNCTION 0
51 LOAD_FAST 0 (a)
54 GET_ITER
55 CALL_FUNCTION 1
58 CALL_FUNCTION 1
61 STORE_FAST 1 (b)
7 64 LOAD_FAST 1 (b)
67 RETURN_VALUE
>>>
</code>
來自：http://python.jobbole.com/86545/
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