今天小編給你推薦30個Python實用的小技巧，你肯定會用到，趕緊來收藏吧！用python做開發？這30個Python實用小技巧你必須掌握！
1、原地交換兩個數字
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
n = 10
print(1 < n < 20)
print(1 > n <= 9)
True
False
3、使用三元操作符來實現條件賦值
[表達式爲真的返回值] if [表達式] else [表達式爲假的返回值]
y = 20
x = 9 if (y == 10) else 8
print(x)
8
找abc中最小的數
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
列表推導
x = [m2 if m>10 else m4 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
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、存儲列表元素到新的變量
testList = [1, 2, 3]
x, y, z = testList # 變量個數應該和列表長度嚴格一致
print(x, y, z)
1 2 3
6、打印引入模塊的絕對路徑
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、交互環境下的“_”操作符
在python控制檯，不論我們測試一個表達式還是調用一個方法，結果都會分配給一個臨時變量“_”
8、字典/集合推導
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、調試腳本
用pdb模塊設置斷點
import pdb
pdb.ste_trace()
10、開啓文件分享
python允許開啓一個HTTP服務器從根目錄共享文件
python -m http.server
11、檢查python中的對象
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']
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、簡化if語句
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、運行時檢測python版本
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、組合多個字符串
test = ["I", "Like", "Python"]
print(test)
print("".join(test))
['I', 'Like', 'Python']
ILikePython
15、四種翻轉字符串、列表的方式
5
3
1
16、用枚舉在循環中找到索引
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
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、從方法中返回多個值
def x():
return 1, 2, 3, 4
a, b, c, d = x()
print(a, b, c, d)
1 2 3 4
19、使用*運算符unpack函數參數
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、用字典來存儲表達式
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、計算任何數的階乘
import functools
result = (lambda k: functools.reduce(int.mul, range(1, k+1), 1))(3)
print(result)
6
22、找到列表中出現次數最多的數
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限制遞歸次數到1000，可以用下面方法重置
import sys
x = 1200
print(sys.getrecursionlimit())
sys.setrecursionlimit(x)
print(sys.getrecursionlimit())
1000
1200
24、檢查一個對象的內存使用
import sys
x = 1
print(sys.getsizeof(x)) # python3.5中一個32比特的整數佔用28字節
28
25、使用slots減少內存開支
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))
減少內存後
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
import sys
lprint = lambda *args: sys.stdout.write(" ".join(map(str, args)))
lprint("python", "tips", 1000, 1001)
python tips 1000 1001
27、從兩個相關序列構建一個字典
t1 = (1, 2, 3)
t2 = (10, 20, 30)
print(dict(zip(t1, t2)))
{1: 10, 2: 20, 3: 30}
28、搜索字符串的多個前後綴
print("http://localhost:8888/notebooks/Untitled6.ipynb".startswith(("http://", "https://")))
print("http://localhost:8888/notebooks/Untitled6.ipynb".endswith((".ipynb", ".py")))
True
True
29、不使用循環構造一個列表
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、實現switch-case語句
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"))