You should use these new features in Python3

An overview of the

As Python2’s official maintenance period comes to an end, more Python projects are switching from Python2 to Python3. However, in the actual work, I found that many people are using Python2 thinking to write Python3 code, Python3 provides us with a lot of new, very convenient features, can help us write code quickly.

F – strings (+ 3.6)

user = "Jane Doe" action = "buy" log_message = 'User {} has logged in and did an action {}.'.format( user, Action) print(log_message) Output: User Jane Doe has logged in and did an action buy.Copy the code

user = "Jane Doe" action = "buy" log_message = f'User {user} has logged in and did an action {action}.' Print (log_message) : User Jane Doe has logged in and did an action buy.Copy the code

Pathlib (+ 3.4)

F-strings is too convenient, but Python provides a more convenient way to handle strings like file strings. Pathlib is a library provided by Python3 that handles file routing. Such as:

From pathlib import Path root = Path('post_sub_folder') print(root) Post_sub_folder path = root/ 'happy_user' print(path.resolve()) : /root/post_sub_folder/happy_userCopy the code

Type hinting (+ 3.5)

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

sentence_has_animal("Donald had a farm without animals")
# True
Copy the code

The Enumerations (+ 3.4)

Python3 provides an Enum class that allows you to easily implement an Enum:

from enum import Enum, auto class Monster(Enum): ZOMBIE = auto() WARRIOR = auto() BEAR = auto() print(monster.zombie) Output: monster.zombieCopy the code

Python3’s Enum also supports comparison and iteration.

For monster in Monster: Print (monster) Output: Monster.zombie Monster.warrior Monster.bearCopy the code

Built – in LRU cache (+ 3.2)

import time def 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: 30.68409967422454sCopy the code

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
Copy the code

Extended iterable unpacking (+ 3.0)

Without further ado, let’s go to the code. The documentation is here

Head, *body, tail = range(5) print(head, body, tail) 0 [1, 2, 3] 4 py, filename, * CMDS = "python3.7 script.py -n 5 -l 15". Split () print(py) print(filename) print(CMDS) Python3.7 script.py ['-n', '5', '-l', '15'] first, _, third, *_ = range(10) print(first, thirdCopy the code

Data classes (+ 3.7)

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 (5.2, "Common armor.", Power () # 10.4 print(armor) # <__main__.Armor object at 0x7fc4800e2cf8>Copy the code

from dataclasses import dataclass @dataclass class Armor: armor: float description: str level: int = 1 def power(self) -> float: Return self. Armor * self. Level = armor (5.2, "Common armor.", Power () # 10.4 print(armor) # armor (description='Common armor.', level=2)Copy the code

Implicit namespace packages (+ 3.3)

Typically, Python recyls the code by packing it into a package (init.py in a directory). The official example is as follows:

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
Copy the code

In Python2, with the same directory structure as above, each directory must have an init.py file, which is called by other modules. In Python3, Implicit Namespace Packages are used instead of __init__.py

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
Copy the code

conclusion