Python中容易被忽视的核心功能总结

import argparse

parser = argparse.ArgumentParser(description="一个简单的命令行工具")
parser.add_argument("--input", help="输入文件路径")
parser.add_argument("--output", help="输出文件路径")
args = parser.parse_args()

if args.input and args.output:
    print(f"从 {args.input} 复制到 {args.output}")

with open("example.txt", "r") as file:
    data = file.read()
# 在离开with块后，文件会被自动关闭

# 列表推导式
squares = [x**2 for x in range(10)]

# 生成器表达式
even_squares = (x**2 for x in range(10) if x % 2 == 0)

data = {}
data.setdefault("count", 0)
data["count"] += 1

def greet(name="World"):
    print(f"Hello, {name}!")

greet()  # 输出 "Hello, World!"
greet("Alice")  # 输出 "Hello, Alice!"

from collections import namedtuple

Person = namedtuple("Person", ["name", "age", "country"])
alice = Person("Alice", 30, "USA")
print(alice.name)  # 输出 "Alice"

a = {1, 2, 3}
b = {3, 4, 5}

union = a | b  # 并集 {1, 2, 3, 4, 5}
intersection = a & b  # 交集 {3}
difference = a - b  # 差集 {1, 2}

from functools import lru_cache

@lru_cache(maxsize=None)  # 缓存所有调用结果
def fib(n):
    if n <= 1:
        return n
    return fib(n-1) + fib(n-2)

fruits = ["apple", "banana", "cherry"]
for index, fruit in enumerate(fruits):
    print(f"Index {index}: {fruit}")

from collections import Counter

data = [1, 2, 2, 3, 3, 3, 4, 4, 4, 4]
count = Counter(data)
print(count[3])  # 输出 3