概述
到2020年,Python2的官方維護(hù)期就要結(jié)束了,越來(lái)越多的Python項(xiàng)目從Python2切換到了Python3。其實(shí)在實(shí)際工作中,很多伙伴都還是在用Python2的思維寫(xiě)Python3的代碼。給大家總結(jié)一下Python3一些新的更方便的特性!希望你們看完后也能高效率的編寫(xiě)代碼
f-strings (3.6+)
在Python里面,我們經(jīng)常使用format函數(shù)來(lái)格式化字符串,例如:
user = "Jane Doe"action = "buy"log_message = 'User {} has logged in and did an action {}.'.format( user, action)print(log_message)輸出:User Jane Doe has logged in and did an action buy.
Python3里面提供了一個(gè)更加靈活方便的方法來(lái)格式化字符串,叫做f-strings。上面的代碼可以這樣實(shí)現(xiàn):
user = "Jane Doe"action = "buy"log_message = f'User {user} has logged in and did an action {action}.'print(log_message)輸出: User Jane Doe has logged in and did an action buy.
Pathlib (3.4+)
f-strings這個(gè)功能太方便了,但是對(duì)于文件路勁這樣的字符串,Python還提供了更加方便的處理方法。Pathlib是Python3提供的一個(gè)處理文件路勁的庫(kù)。例如:
from pathlib import Pathroot = Path('post_sub_folder')print(root)輸出結(jié)果: post_sub_folder path = root / 'happy_user'# 輸出絕對(duì)路勁print(path.resolve())輸出結(jié)果:/root/post_sub_folder/happy_user
Type hinting (3.5+)
靜態(tài)與動(dòng)態(tài)類型是軟件工程中的一個(gè)熱門(mén)話題,每個(gè)人都有不同的看法,Python作為一個(gè)動(dòng)態(tài)類型語(yǔ)言,在Python3中也提供了Type hinting功能,例如:
def sentence_has_animal(sentence: str) -> bool: return "animal" in sentence sentence_has_animal("Donald had a farm without animals")# True
Enumerations (3.4+)
Python3提供的Enum類讓你很容就能實(shí)現(xiàn)一個(gè)枚舉類型:
from enum import Enum, autoclass Monster(Enum): ZOMBIE = auto() WARRIOR = auto() BEAR = auto()print(Monster.ZOMBIE)輸出: Monster.ZOMBIE
Python3的Enum還支持比較和迭代。
for monster in Monster: print(monster)輸出: Monster.ZOMBIE Monster.WARRIOR Monster.BEAR
Built-in LRU cache (3.2+)
緩存是現(xiàn)在的軟件領(lǐng)域經(jīng)常使用的技術(shù),Python3提供了一個(gè)lru_cache裝飾器,來(lái)讓你更好的使用緩存。下面有個(gè)實(shí)例:
import timedef fib(number: int) -> int: if number == 0: return 0 if number == 1: return 1 return fib(number-1) + fib(number-2)start = time.time()fib(40)print(f'Duration: {time.time() - start}s')# Duration: 30.684099674224854s
現(xiàn)在我們可以使用lru_cache來(lái)優(yōu)化我們上面的代碼,降低代碼執(zhí)行時(shí)間。
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) + fib_memoization(number-2)start = time.time()fib_memoization(40)print(f'Duration: {time.time() - start}s')# Duration: 6.866455078125e-05s
Extended iterable unpacking (3.0+)
代碼如下:
head, *body, tail = range(5)print(head, body, tail)輸出: 0 [1, 2, 3] 4py, filename, *cmds = "python3.7 script.py -n 5 -l 15".split()print(py)print(filename)print(cmds)輸出:python3.7 script.py ['-n', '5', '-l', '15']first, _, third, *_ = range(10)print(first, third)輸出: 0 2
Data classes (3.7+)
Python3提供data class裝飾器來(lái)讓我們更好的處理數(shù)據(jù)對(duì)象,而不用去實(shí)現(xiàn) init () 和 repr() 方法。假設(shè)如下的代碼:
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()# 10.4print(armor)# <__main__.Armor object at 0x7fc4800e2cf8>
使用data class實(shí)現(xiàn)上面功能的代碼,這么寫(xiě):
from dataclasses import dataclass@dataclassclass 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()# 10.4print(armor)# Armor(armor=5.2, description='Common armor.', level=2)
Implicit namespace packages (3.3+)
通常情況下,Python通過(guò)把代碼打成包(在目錄中加入 init .py實(shí)現(xiàn))來(lái)復(fù)用,官方給的示例如下:
sound/ Top-level package __init__.py Initialize the sound package formats/ Subpackage for file format conversions __init__.py wavread.py wavwrite.py aiffread.py aiffwrite.py auread.py auwrite.py ... effects/ Subpackage for sound effects __init__.py echo.py surround.py reverse.py ... filters/ Subpackage for filters __init__.py equalizer.py vocoder.py karaoke.py
在Python2里,如上的目錄結(jié)構(gòu),每個(gè)目錄都必須有 init .py文件,一遍其他模塊調(diào)用目錄下的python代碼,在Python3里,通過(guò) Implicit Namespace Packages可是不使用__init__.py文件
sound/ Top-level package __init__.py Initialize the sound package formats/ Subpackage for file format conversions wavread.py wavwrite.py aiffread.py aiffwrite.py auread.py auwrite.py ... effects/ Subpackage for sound effects echo.py surround.py reverse.py ... filters/ Subpackage for filters equalizer.py vocoder.py karaoke.py
結(jié)語(yǔ)
這里由于時(shí)間關(guān)系(確實(shí)挺忙)只列出了部分Python3的新功能,希望你在看了這篇文章以后,學(xué)以致用,寫(xiě)出更清晰更直觀的代碼!
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