python3 新特性

Posted 2021-12-10 hotsnow

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:

1 2 3 4

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:

1 2 3 4 5 6 7 8 9 10 11 12 13 14

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:

1 2 3 4 5 6 7 8 9

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

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‘)

 

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。

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()

 

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)