标准库 #

import os

# 环境变量
print(os.environ)
print(os.getenv('HOME'))

# 文件和目录
os.getcwd()           # 当前目录
os.chdir('/path')     # 切换目录
os.listdir('.')       # 列出目录内容
os.mkdir('new_dir')   # 创建目录
os.makedirs('a/b/c')  # 递归创建目录
os.rmdir('dir')       # 删除空目录
os.remove('file.txt') # 删除文件
os.rename('old', 'new')  # 重命名

# 路径操作
os.path.exists('file.txt')    # 是否存在
os.path.isfile('file.txt')    # 是否是文件
os.path.isdir('dir')          # 是否是目录
os.path.join('a', 'b', 'c')   # 拼接路径
os.path.split('/a/b/c.txt')   # ('/a/b', 'c.txt')
os.path.splitext('file.txt')  # ('file', '.txt')

import sys

print(sys.version)     # Python版本
print(sys.path)        # 模块搜索路径
print(sys.argv)        # 命令行参数
sys.exit(0)            # 退出程序

import math

print(math.pi)         # 3.14159...
print(math.e)          # 2.71828...
print(math.sqrt(16))   # 4.0
print(math.ceil(3.2))  # 4
print(math.floor(3.8)) # 3
print(math.log(10))    # 自然对数
print(math.log10(100)) # 2.0
print(math.sin(math.pi/2))  # 1.0

import random

print(random.random())           # 0.0-1.0随机浮点数
print(random.randint(1, 10))     # 1-10随机整数
print(random.choice([1, 2, 3]))  # 随机选择
print(random.sample([1,2,3], 2)) # 随机抽样
random.shuffle([1, 2, 3])        # 打乱顺序

from datetime import datetime, date, time, timedelta

# 当前时间
now = datetime.now()
today = date.today()

# 创建日期时间
d = date(2024, 3, 16)
t = time(10, 30, 0)
dt = datetime(2024, 3, 16, 10, 30, 0)

# 格式化
print(now.strftime('%Y-%m-%d %H:%M:%S'))

# 解析
dt = datetime.strptime('2024-03-16', '%Y-%m-%d')

# 时间差
delta = timedelta(days=7)
future = now + delta

import json

# 编码
data = {"name": "Tom", "age": 25}
json_str = json.dumps(data)
json_str = json.dumps(data, indent=2)  # 格式化

# 解码
data = json.loads(json_str)

# 文件操作
with open('data.json', 'w') as f:
    json.dump(data, f)

with open('data.json') as f:
    data = json.load(f)

import re

# 匹配
match = re.match(r'(\d+)', '123abc')
print(match.group(1))  # '123'

# 搜索
match = re.search(r'(\d+)', 'abc123')
print(match.group(1))  # '123'

# 查找所有
numbers = re.findall(r'\d+', 'a1b2c3')  # ['1', '2', '3']

# 替换
result = re.sub(r'\d+', 'X', 'a1b2c3')  # 'aXbXcX'

# 分割
parts = re.split(r'\s+', 'a b  c')  # ['a', 'b', 'c']

from collections import Counter, defaultdict, OrderedDict

# Counter计数器
counter = Counter('hello')
print(counter)  # Counter({'l': 2, 'h': 1, 'e': 1, 'o': 1})

# defaultdict默认值
d = defaultdict(list)
d['key'].append('value')

# OrderedDict有序字典
od = OrderedDict()

import itertools

# 无限迭代器
for i in itertools.count(10, 2):
    if i > 20: break
    print(i)

# 循环迭代
for item in itertools.cycle([1, 2, 3]):
    break

# 排列组合
list(itertools.permutations([1, 2, 3], 2))  # 排列
list(itertools.combinations([1, 2, 3], 2))  # 组合

# 链接迭代器
list(itertools.chain([1, 2], [3, 4]))  # [1, 2, 3, 4]

from functools import reduce, partial, lru_cache

# reduce归约
result = reduce(lambda x, y: x + y, [1, 2, 3, 4])  # 10

# partial偏函数
def power(base, exponent):
    return base ** exponent

square = partial(power, exponent=2)
print(square(5))  # 25

# lru_cache缓存
@lru_cache(maxsize=128)
def fibonacci(n):
    if n <= 1:
        return n
    return fibonacci(n-1) + fibonacci(n-2)