【Python | 进阶】提高你的Python技能，99个让代码更简洁、更快的秘密技巧， 确定不来看看？

for i, v in enumerate(list_name):
    print(i, v)

from collections import defaultdict

d = defaultdict(list) # 默认值
d['a'].append(1) 
print(d) # {'a': [1]}

names = ['a', 'b']
ages = [20, 30]

for name, age in zip(names, ages): # 变成元组对
    print(name, age)

for i in reversed(range(1, 10)):
    print(i) 

list_with_duplicates = [1, 2, 1, 3]
list_without_duplicates = list(set(list_with_duplicates))

with open('file.txt') as f:
    data = f.read()

squares = [x**2 for x in range(1, 6)]
print(squares)  # [1, 4, 9, 16, 25]

squares = {x: x**2 for x in range(1, 6)}
print(squares)  # {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

def uppercase_decorator(func):
    def wrapper():
        result = func()
        return result.upper()
    return wrapper

@uppercase_decorator # 实现一个大写装饰器，对所有返回为string的大写
def greet():
    return "hello"

print(greet())  # "HELLO"

def fibonacci():
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b

fib = fibonacci()
print(next(fib))  # 0
print(next(fib))  # 1
print(next(fib))  # 1
print(next(fib))  # 2

from collections import Counter

fruits = ['apple', 'banana', 'orange', 'apple', 'banana', 'apple']
fruit_counts = Counter(fruits)
print(fruit_counts)

# 输出：
# Counter({'apple': 3, 'banana': 2, 'orange': 1})

import itertools

# 排列组合
letters = ['a', 'b', 'c']
perms = itertools.permutations(letters, 2)
print(list(perms))  # [('a', 'b'), ('a', 'c'), ('b', 'a'), ('b', 'c'), ('c', 'a'), ('c', 'b')]

# 无限迭代器
count = itertools.count(start=1, step=2)
print(next(count))  # 1
print(next(count))  # 3
print(next(count))  # 5

import logging

logging.basicConfig(level=logging.DEBUG, format='%(asctime)s - %(levelname)s - %(message)s')
logging.debug('This is a debug message')
logging.info('This is an info message')
logging.warning('This is a warning message')
logging.error('This is an error message')
logging.critical('This is a critical message')

my_list = [None] * 3
print(my_list)

[None, None, None]

def main():
    print("Running as main program")

if __name__ == "__main__":
    main()

module_name = input("Enter module name: ")
module = __import__(module_name)

x = 50  

print(locals()) 
# {'x': 50}

print(globals())
# {'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x7f9c4c4c4e80>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, 'x': 50}

import sys

sys.setrecursionlimit(2000)

import os
print(os.name)

# 等同于

print(__import__('os').name)

def func():
    __tracebackhide__ = True 
    raise Exception("hidden")

func()  # No traceback 

if __debug__:
    print("Running in debug mode")

class Meta(type):
    pass

class MyClass(object):
    __metaclass__ = Meta

class Point:
    def __del__(self):
        print("Point destroyed")

class Point:
    def __getattr__(self, attr):
        ...
    def __setattr__(self, attr, value): 
        ...

class Point:
    def __iter__(self):
        ... 
    def __next__(self):
        ...

class Point:
    def __enter__(self):
        ...
    def __exit__(self, exc_type, exc_value, traceback):
        ...

print(1,2,3)
# 1 2 3

print("{:10}".format(123)) 
# "       123"
print("{:^10}".format(123))  
# "   123    " 
print("{:*>10}".format(123))
# "*****123"

" Hello".startswith("H") 
# True
"Hello".endswith("o")
# True

d = {"name": "John"}
d.get("name")    # John
d.get("age")     # None

for n in range(2, 10):
   for x in range(2, n):
      if n % x == 0:
         break
   else:
       print(n)