Python的幾個高級編程技巧

Python有一些技巧對你來講是新知識，可是還有一些技巧會讓你的代碼效率大幅提高。

本文總結了一下本身用到的一些Python高級編程技巧，但願對你們有幫助。

列表生成器

a=[1,2,3]
[x*x for x in a if x>1]

[4, 9]

集合生成器

a=[1,2,3]
s = {x*x for x in a if x>1}
s

{4, 9}

type(s)

set

字典生成器

a=[1,2,3]
{str(x):x+1 for x in a if x>1}

{'2': 3, '3': 4}

range

list(range(10))

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

list(range(3,10))

[3, 4, 5, 6, 7, 8, 9]

filter用於過濾數據

list(filter(lambda x:x%3==0, range(10)))

[0, 3, 6, 9]

collections.namedtuple給列表或者元組命名

from collections import namedtuple
Point = namedtuple('Point', ['x', 'y'])
p = Point(11, 22)

p.x

11

p.y

22

random的使用

from random import randint
randint(1,10)

1

統計序列元素的頻度和TOP N

from collections import Counter
c = Counter('aaabbbbccccccddddddeeeeee')

c

Counter({'a': 3, 'b': 4, 'c': 6, 'd': 6, 'e': 6})

c.most_common(3)

[('c', 6), ('d', 6), ('e', 6)]

將字典按value排序

from random import randint
keys = 'abcdefg'
d = {x:randint(90,100) for x in keys}

d

{'a': 90, 'b': 98, 'c': 100, 'd': 97, 'e': 95, 'f': 93, 'g': 92}

d.items()

dict_items([('a', 90), ('b', 98), ('c', 100), ('d', 97), ('e', 95), ('f', 93), ('g', 92)])

sorted(d.items(), key=lambda x : x[1])

[('a', 90), ('g', 92), ('f', 93), ('e', 95), ('d', 97), ('b', 98), ('c', 100)]

得到多個詞典的key的交集

from random import randint, sample
dd1 = {x:randint(90,100) for x in sample('abcdefghij', 5)}
dd2 = {x:randint(90,100) for x in sample('abcdefghij', 5)}
dd3 = {x:randint(90,100) for x in sample('abcdefghij', 5)}

dd1

{'h': 99, 'f': 94, 'c': 91, 'i': 99, 'b': 95}

dd2

{'b': 95, 'g': 91, 'h': 98, 'f': 100, 'd': 92}

dd3

{'h': 95, 'g': 99, 'a': 100, 'd': 96, 'i': 92}

mp = map(dict.keys, (dd1, dd2, dd3))

list(mp)

[dict_keys(['h', 'f', 'c', 'i', 'b']),
 dict_keys(['b', 'g', 'h', 'f', 'd']),
 dict_keys(['h', 'g', 'a', 'd', 'i'])]

from functools import reduce
reduce(lambda x,y: x&y, mp)

{'h'}

怎樣讓字典按照插入有序

from collections import OrderedDict
d = OrderedDict()
d['x'] = 1
d['y'] = 2
d['a'] = 2
d['b'] = 2
d

OrderedDict([('x', 1), ('y', 2), ('a', 2), ('b', 2)])

怎樣實現長度爲N的隊列功能

from collections import deque
d = deque([], 3)
d.append(1)
d.append(2)
d.append(3)
d.append(4)
d

deque([2, 3, 4])

怎樣同時遍歷多個集合

names = [x for x in 'abcdefg']
ages = [x for x in range(21, 28)]
scores = [randint(90,100) for x in range(7)]

for name,age,score in zip(names, ages, scores):
    print(name,age,score)

a 21 95
b 22 99
c 23 94
d 24 95
e 25 100
f 26 96
g 27 95

怎樣串行的遍歷多個集合

lista = (randint(1,10) for x in range(10))
listb = [randint(90,100) for x in range(20)]

from itertools import chain

for x in chain(lista, listb):
    print(x, end=',')

5,10,3,1,8,7,6,5,6,8,92,95,91,98,95,93,96,95,94,98,92,90,91,91,99,96,90,100,94,99,

使用多種分隔符替換字符串

s = 'a,b;c/d'
import re
re.sub(r'[,;/]', '-', s)

'a-b-c-d'

字符串的模糊搜索與部分替換

s = 'things happend in 2017-08-09, it is a sunddy'
re.sub(r'(\d{4})-(\d{2})-(\d{2})', r'\2-\1-\3', s)

'things happend in 08-2017-09, it is a sunddy'

列表JOIN時若是有數字元素怎麼辦

print('\t'.join([str(x) for x in ['a','b',33,4.0,'e']]))

a   b   33  4.0 e

如何使用多線程-方法1

from threading import Thread

def func(x):
    print(x, x*x*x)

ts = []
for x in range(10):
    t = Thread(target=func, args=(x,))
    t.start()
    ts.append(t)

for t in ts:
    t.join()

print('main thread over')

0 0
1 1
2 8
3 27
4 64
5 125
6 216
7 343
8 512
9 729
main thread over

如何使用多線程-方法2

如下的輸出錯亂，是正常的，由於多個線程同時print就錯亂了

from threading import Thread

class MyThread(Thread):
    def __init__(self, x):
        Thread.__init__(self)
        self.x = x

    def run(self):
        print(self.x, self.x*self.x*self.x)


ts = []
for x in range(10):
    t = MyThread(x)
    t.start()
    ts.append(t)

for t in ts:
    t.join()

print('main thread over')

0 0
1 1
2 3 27
8
45 64
6 216
 125
7 343
8 512
9 729
main thread over

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