python3 新特性

2020/12 31 18:12

1、格式化字符串f-string

user = "Mike"
log_message = f'User{user} has logged in'

2、路径管理库Pathlib

3、类型提示Type hinting

def sentence_has_animal(sentence:str) -> bool:
return "animal" in sentence

4、枚举类enum

from enum import Enum, auto, unique
@unique #装饰器去重复
class monster(Enum):
zombie = auto()
warrior = auto()
bear = auto()

5、itertools模块

无限迭代器代码如下:

迭代器 参数 结果 例子
count() start, [step] start, start+step, start+2*step, ... count(10) --> 10 11 12 13 14 ...
cycle() p p0, p1, ... plast, p0, p1, ... cycle('ABCD') --> A B C D A B C D ...
repeat() elem [,n] elem, elem, elem, ... endlessly or up to n times repeat(10, 3) --> 10 10 10

处理输入序列迭代器代码如下:

迭代器 参数 结果 例子
chain() p, q, ... p0, p1, ... plast, q0, q1, ... chain('ABC', 'DEF') --> A B C D E F
compress() data, selectors (d[0] if s[0] ), (d[1] if s[1] ), ... compress('ABCDEF', [1,0,1,0,1,1] ) --> A C E F
dropwhile() pred, seq seq[n] , seq[n+1] , starting when pred fails dropwhile(lambda x: x<5, [1,4,6,4,1] ) --> 6 4 1
groupby() iterable[, keyfunc] sub-iterators grouped by value of keyfunc(v)
ifilter() pred, seq elements of seq where pred(elem) is True ifilter(lambda x: x%2, range(10)) --> 1 3 5 7 9
ifilterfalse() pred, seq elements of seq where pred(elem) is False ifilterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8
islice() seq, [start,] stop [, step] elements from seq[start:stop:step] islice('ABCDEFG', 2, None) --> C D E F G
imap() func, p, q, ... func(p0, q0), func(p1, q1), ... imap(pow, (2,3,10), (5,2,3)) --> 32 9 1000
starmap() func, seq func(*seq[0] ), func(*seq[1] ), ... starmap(pow, [(2,5), (3,2), (10,3)] ) --> 32 9 1000
tee() it, n it1, it2 , ... itn splits one iterator into n
takewhile() pred, seq seq[0] , seq[1] , until pred fails takewhile(lambda x: x<5, [1,4,6,4,1] ) --> 1 4
izip() p, q, ... (p[0] , q[0] ), (p[1] , q[1] ), ... izip('ABCD', 'xy') --> Ax By
izip_longest() p, q, ... (p[0] , q[0] ), (p[1] , q[1] ), ... izip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-

组合生成器代码如下:

迭代器 参数 结果
product() p, q, ... [repeat=1] cartesian product, equivalent to a nested for-loop
permutations() p[, r] r-length tuples, all possible orderings, no repeated elements
combinations() p, r r-length tuples, in sorted order, no repeated elements
combinations_with_replacement() p, r r-length tuples, in sorted order, with repeated elements
product('ABCD', repeat=2) AA AB AC AD BA BB BC BD CA CB CC CD DA DB DC DD
permutations('ABCD', 2) AB AC AD BA BC BD CA CB CD DA DB DC
combinations('ABCD', 2) AB AC AD BC BD CD
combinations_with_replacement('ABCD', 2) AA AB AC AD BB BC BD CC CD DD
6、LRU缓存,memoization技术

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from functools import lru_cache
@lru_cache(maxsize=512)
def fib_memoization(number:int) -> int:
if number ==0 : return 0
if number ==1 : return 1
return fib_memoization(number - 1)
start = time.time()
fib_memoization(40)
print(f'Duration:{time.time() - start}s')
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7、可扩展的可迭代对象解包

head, *bodey, tail = range(5) # 0, [1,2,3] , 4

8、Data class装饰器,用来减少对样板代码的使用,该装饰器会自动生成__init()__和__repr()__方法。

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class Armor:
def __init__(self, armor:float, description:str, level:int = 1):
self.armor = armor
self.level = level
self.description = description

def power(self) -> float:
return self.armor * self.level

armor = Armor(5.2, "common armor.", 2)
armor.power() #10.4

###使用Data Class实现相同的Armor类
from dataclasses import dataclass
@dataclass
class Armor:
armor : float
description : str
level : int = 1

def power(self) -> float:
return self.armor *self.level

armor = Armor(5.2, "common armor.", 2)
armor.power()
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9、bisect模块保持列表排序:

这是一个免费的二分查找实现和快速插入有序序列的工具。也就是说,你可以使用:

import bisect
bisect.insort(list, element)

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