?1、原地交換兩個(gè)數(shù)字
| 1 2 3 4 | x,?y?=10,?20
print(x,?y)
y,?x?=?x,?y
print(x,?y)
|
10 20
20 10
2、鏈狀比較操作符
| 1 2 3 | n?=?10
print(1?<?n?<?20)
print(1?>?n?<=?9)
|
True
False
3、使用三元操作符來實(shí)現(xiàn)條件賦值
[表達(dá)式為真的返回值] if [表達(dá)式] else [表達(dá)式為假的返回值]
| 1 2 3 | y?=?20
x?=?9?if?(y?==?10)?else?8
print(x)
|
8
# 找abc中最小的數(shù)
| 1 2 3 4 5 6 | def?small(a,?b,?c):
????return?a?if?a<b?and?a<c?else?(b?if?b<a?and?b<c?else?c)
print(small(1,?0,?1))
print(small(1,?2,?2))
print(small(2,?2,?3))
print(small(5,?4,?3))
|
0
1
3
3
| 1 2 3 | #?列表推導(dǎo)
x?=?[m**2?if?m>10?else?m**4?for?m?in?range(50)]
print(x)
|
[0, 1, 16, 81, 256, 625, 1296, 2401, 4096, 6561, 10000, 121, 144, 169, 196, 225, 256, 289, 324, 361, 400, 441, 484, 529, 576, 625, 676, 729, 784, 841, 900, 961, 1024, 1089, 1156, 1225, 1296, 1369, 1444, 1521, 1600, 1681, 1764, 1849, 1936, 2025, 2116, 2209, 2304, 2401]
4、多行字符串
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | multistr?=?"select?*?from?multi_row?\
where?row_id?<?5"
print(multistr)
select?*?from?multi_row?where?row_id?<?5
multistr?=?"""select?*?from?multi_row
where?row_id?<?5"""
print(multistr)
select?*?from?multi_row
where?row_id?<?5
multistr?=?("select?*?from?multi_row"
"where?row_id?<?5"
"order?by?age")
print(multistr)
select?*?from?multi_rowwhere?row_id?<?5order?by?age
|
5、存儲(chǔ)列表元素到新的變量
| 1 2 3 | testList?=?[1,?2,?3]
x,?y,?z?=?testList????#?變量個(gè)數(shù)應(yīng)該和列表長(zhǎng)度嚴(yán)格一致
print(x,?y,?z)
|
1 2 3
6、打印引入模塊的絕對(duì)路徑
| 1 2 3 4 5 6 | import?threading
import?socket
print(threading)
print(socket)
<module?'threading'?from?'d:\\python351\\lib\\threading.py'>
<module?'socket'?from?'d:\\python351\\lib\\socket.py'>
|
7、交互環(huán)境下的“_”操作符
在python控制臺(tái)，不論我們測(cè)試一個(gè)表達(dá)式還是調(diào)用一個(gè)方法，結(jié)果都會(huì)分配給一個(gè)臨時(shí)變量“_”
8、字典/集合推導(dǎo)
| 1 2 3 4 | testDic?=?{i:?i?*?i?for?i?in?range(10)}
testSet?=?{i?*?2?for?i?in?range(10)}
print(testDic)
print(testSet)
|
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}
{0, 2, 4, 6, 8, 10, 12, 14, 16, 18}
9、調(diào)試腳本
用pdb模塊設(shè)置斷點(diǎn)
| 1 2 | import?pdb
pdb.ste_trace()
|
10、開啟文件分享
python允許開啟一個(gè)HTTP服務(wù)器從根目錄共享文件
11、檢查python中的對(duì)象
| 1 2 | test?=?[1,?3,?5,?7]
print(dir(test))
|
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
| 1 2 | test?=?range(10)
print(dir(test))
|
['__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'count', 'index', 'start', 'step', 'stop']
12、簡(jiǎn)化if語句
| 1 2 3 4 | #?use?following?way?to?verify?multi?values
if?m?in?[1,?2,?3,?4]:
#?do?not?use?following?way
if?m==1?or?m==2?or?m==3?or?m==4:
|
13、運(yùn)行時(shí)檢測(cè)python版本
| 1 2 3 4 | import?sys
if?not?hasattr(sys,?"hexversion")?or?sys.version_info?!=?(2,?7):
????print("sorry,?you?are?not?running?on?python?2.7")
????print("current?python?version:",?sys.version)
|
sorry, you are not running on python 2.7
current python version: 3.5.1 (v3.5.1:37a07cee5969, Dec? 6 2015, 01:54:25) [MSC v.1900 64 bit (AMD64)]
14、組合多個(gè)字符串
| 1 2 3 | test?=?["I",?"Like",?"Python"]
print(test)
print("".join(test))
|
['I', 'Like', 'Python']
ILikePython
15、四種翻轉(zhuǎn)字符串、列表的方式
5
3
1
16、用枚舉在循環(huán)中找到索引
| 1 2 3 | test?=?[10,?20,?30]
for?i,?value?in?enumerate(test):
????print(i,?':',?value)
|
0 : 10
1 : 20
2 : 30
17、定義枚舉量
| 1 2 3 4 5 6 | class?shapes:
????circle,?square,?triangle,?quadrangle?=?range(4)
print(shapes.circle)
print(shapes.square)
print(shapes.triangle)
print(shapes.quadrangle)
|
0
1
2
3
18、從方法中返回多個(gè)值
| 1 2 3 4 | def?x():
????return?1,?2,?3,?4
a,?b,?c,?d?=?x()
print(a,?b,?c,?d)
|
1 2 3 4
19、使用*運(yùn)算符unpack函數(shù)參數(shù)
| 1 2 3 4 5 6 7 | def?test(x,?y,?z):
????print(x,?y,?z)
testDic?=?{'x':1,?'y':2,?'z':3}
testList?=?[10,?20,?30]
test(*testDic)
test(**testDic)
test(*testList)
|
z x y
1 2 3
10 20 30
20、用字典來存儲(chǔ)表達(dá)式
| 1 2 3 4 5 6 | stdcalc?=?{
????"sum":?lambda?x,?y:?x?+?y,
????"subtract":?lambda?x,?y:?x?-?y
}
print(stdcalc["sum"](9,?3))
print(stdcalc["subtract"](9,?3))
|
12
6
21、計(jì)算任何數(shù)的階乘
| 1 2 3 | import?functools
result?=?(lambda?k:?functools.reduce(int.__mul__,?range(1,?k+1),?1))(3)
print(result)
|
6
22、找到列表中出現(xiàn)次數(shù)最多的數(shù)
| 1 2 | test?=?[1,?2,?3,?4,?2,?2,?3,?1,?4,?4,?4,?4]
print(max(set(test),?key=test.count))
|
4
23、重置遞歸限制
python限制遞歸次數(shù)到1000，可以用下面方法重置
| 1 2 3 4 5 | import?sys
x?=?1200
print(sys.getrecursionlimit())
sys.setrecursionlimit(x)
print(sys.getrecursionlimit())
|
1000
1200
24、檢查一個(gè)對(duì)象的內(nèi)存使用
| 1 2 3 | import?sys
x?=?1
print(sys.getsizeof(x))????#?python3.5中一個(gè)32比特的整數(shù)占用28字節(jié)
|
28
25、使用slots減少內(nèi)存開支
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | import?sys
#?原始類
class?FileSystem(object):
????def?__init__(self,?files,?folders,?devices):
????????self.files?=?files
????????self.folder?=?folders
????????self.devices?=?devices
print(sys.getsizeof(FileSystem))
#?減少內(nèi)存后
class?FileSystem(object):
????__slots__?=?['files',?'folders',?'devices']
????def?__init__(self,?files,?folders,?devices):
????????self.files?=?files
????????self.folder?=?folders
????????self.devices?=?devices
print(sys.getsizeof(FileSystem))
|
1016
888
26、用lambda 來模仿輸出方法
| 1 2 3 | import?sys
lprint?=?lambda?*args:?sys.stdout.write("?".join(map(str,?args)))
lprint("python",?"tips",?1000,?1001)
|
python tips 1000 1001
27、從兩個(gè)相關(guān)序列構(gòu)建一個(gè)字典
| 1 2 3 | t1?=?(1,?2,?3)
t2?=?(10,?20,?30)
print(dict(zip(t1,?t2)))
|
{1: 10, 2: 20, 3: 30}
28、搜索字符串的多個(gè)前后綴
| 1 2 | print("http://localhost:8888/notebooks/Untitled6.ipynb".startswith(("http://",?"https://")))
print("http://localhost:8888/notebooks/Untitled6.ipynb".endswith((".ipynb",?".py")))
|
True
True
29、不使用循環(huán)構(gòu)造一個(gè)列表
| 1 2 3 4 | import?itertools
import?numpy?as?np
test?=?[[-1,?-2],?[30,?40],?[25,?35]]
print(list(itertools.chain.from_iterable(test)))
|
[-1, -2, 30, 40, 25, 35]
30、實(shí)現(xiàn)switch-case語句
| 1 2 3 4 5 | def?xswitch(x):
????return??xswitch._system_dict.get(x,?None)
xswitch._system_dict?=?{"files":10,?"folders":5,?"devices":2}
print(xswitch("default"))
print(xswitch("devices"))
|
None
