Python学习教程_Python学习路线：Python3里你不知道的秘密特性
概述
到2020年，Python2的官方维护期就要结束了，越来越多的Python项目从Python2切换到了Python3。其实在实际工作中，很多伙伴都还是在用Python2的思维写Python3的代码。给大家总结一下Python3一些新的更方便的特性！希望你们看完后也能高效率的编写代码
f-strings (3.6+)
在Python里面，我们经常使用format函数来格式化字符串，例如：
user = "Jane Doe"action = "buy"log_message = 'User {} has logged in and did an action {}.'.format(
user,
action)print(log_message)输出：User Jane Doe has logged in and did an action buy.
Python3里面提供了一个更加灵活方便的方法来格式化字符串，叫做f-strings。上面的代码可以这样实现:
user = "Jane Doe"action = "buy"log_message = f'User {user} has logged in and did an action {action}.'print(log_message)输出: User Jane Doe has logged in and did an action buy.
Pathlib (3.4+)
f-strings这个功能太方便了，但是对于文件路劲这样的字符串，Python还提供了更加方便的处理方法。Pathlib是Python3提供的一个处理文件路劲的库。例如：
from pathlib import Pathroot = Path('post_sub_folder')print(root)输出结果: post_sub_folder
path = root / 'happy_user'# 输出绝对路劲print(path.resolve())输出结果：/root/post_sub_folder/happy_user
Type hinting (3.5+)
静态与动态类型是软件工程中的一个热门话题，每个人都有不同的看法，Python作为一个动态类型语言，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类让你很容就能实现一个枚举类型：
from enum import Enum, autoclass Monster(Enum): ZOMBIE = auto() WARRIOR = auto() BEAR = auto()print(Monster.ZOMBIE)输出: Monster.ZOMBIE
Python3的Enum还支持比较和迭代。
for monster in Monster: print(monster)输出: Monster.ZOMBIE Monster.WARRIOR Monster.BEAR
Built-in LRU cache (3.2+)
缓存是现在的软件领域经常使用的技术，Python3提供了一个lru_cache装饰器，来让你更好的使用缓存。下面有个实例：
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
现在我们可以使用lru_cache来优化我们上面的代码，降低代码执行时间。
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+)
代码如下：
head, *body, tail = range(5)print(head, body, tail)输出： 0 [1, 2, 3] 4py, filename, *cmds = "python3.7 script.py -n 5 -l 15".split()print(py)print(filename)print(cmds)输出：python3.7 script.py ['-n', '5', '-l', '15']first, _, third, *_ = range(10)print(first, third)输出： 0 2
Data classes (3.7+)
Python3提供data class装饰器来让我们更好的处理数据对象，而不用去实现 init () 和 repr() 方法。假设如下的代码:
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实现上面功能的代码，这么写:
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+)
通常情况下，Python通过把代码打成包（在目录中加入 init .py实现）来复用，官方给的示例如下:
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，如上的目录结构，每个目录都必须有 init .py文件，一遍其他模块调用目录下的python代码，在Python3里，通过 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
结语
这里由于时间关系（确实挺忙
）只列出了部分Python3的新功能，希望你在看了这篇文章以后，学以致用，写出更清晰更直观的代码！更多的Python学习教程和分享，后续会继续为大家更新！