Python常用内置标准库超详细学习笔记

from datetime import datetime, timedelta
# 1. 获取当前时间
now = datetime.now()
print(f"当前时间: {now}")
# 2. 格式化输出 (strftime)
print(now.strftime("%Y-%m-%d %H:%M:%S")) # 2023-10-27 14:30:05
# 3. 字符串转时间对象 (strptime)
date_str = "2023-01-01"
dt_obj = datetime.strptime(date_str, "%Y-%m-%d")
# 4. 时间计算 (timedelta)
yesterday = now - timedelta(days=1)
future = now + timedelta(hours=2)

import math
print(math.pi)        # 圆周率 3.14159...
print(math.sqrt(16))  # 开平方 4.0
print(math.ceil(3.1)) # 向上取整 4

import random
print(random.random())       # 0到1之间的浮点数
print(random.randint(1, 10)) # 1到10之间的随机整数（含10）
fruits = ["苹果", "香蕉", "橙子"]
print(random.choice(fruits)) # 随机选一个
items = [1, 2, 3, 4, 5]
random.shuffle(items)        # 打乱列表顺序

import json
data = {"name": "Jojo", "age": 25, "is_admin": False}
# 1. 编码：字典 -> JSON 字符串 (dumps)
json_str = json.dumps(data, indent=4) # indent让输出更漂亮
# 2. 解码：JSON 字符串 -> 字典 (loads)
parsed_data = json.loads(json_str)
# 3. 处理文件 (dump/load)
with open("config.json", "w") as f:
    json.dump(data, f) # 直接写入文件

import sys
# 1. 获取命令行参数 (常用语脚本传参)
# 运行命令: python script.py arg1 arg2
print(sys.argv) 
# 2. 退出程序
# sys.exit(0) # 0表示正常退出
# 3. 模块搜索路径
# print(sys.path) 
# 4. 查看系统平台
print(sys.platform) # win32, darwin(Mac), linux

from collections import Counter, defaultdict
# Counter 示例：统计词频
text = "apple banana apple orange apple banana"
counts = Counter(text.split())
print(counts) # Counter({'apple': 3, 'banana': 2, 'orange': 1})
print(counts.most_common(1)) # 获取出现次数最多的
# defaultdict 示例
d = defaultdict(int) # 默认值为 0
d["count"] += 1      # 不会报错，直接从0加到1

import re
text = "我的邮箱是 jojo_123@example.com，请联系我。"
# 匹配邮箱的简单正则
pattern = r'[a-zA-Z0-9_]+@[a-zA-Z0-9]+\.[a-zA-Z]+'
# 搜索
match = re.search(pattern, text)
if match:
    print(f"找到邮箱: {match.group()}")
# 替换
clean_text = re.sub(pattern, "[HIDDEN]", text)
print(clean_text)