基本文件读写
with open('file.txt', 'w') as f:
f.write('Hello, World!')
with open('file.txt', 'r') as f:
content = f.read()路径处理
import os
from pathlib import Path
file_path = os.path.join('folder', 'file.txt')
path = Path('folder') / 'file.txt' # 现代写法压缩 / 解压缩文件
import zipfile
with zipfile.ZipFile('archive.zip', 'w') as zipf:
zipf.write('file.txt')
with zipfile.ZipFile('archive.zip', 'r') as zipf:
zipf.extractall('extracted')列表推导式
squares = [x**2 for x in range(10)]
even_squares = [x**2 for x in range(10) if x % 2 == 0]集合操作
a = {1, 2, 3, 4}
b = {3, 4, 5, 6}
print(a.union(b)) # 并集: {1, 2, 3, 4, 5, 6}
print(a.intersection(b)) # 交集: {3, 4}字符串格式化
name, age = "Alice", 30
print(f"{name}今年{age}岁") # f-string
print("{0}今年{1}岁".format(name, age))正则表达式
import re
text = "联系方式: email@example.com 电话123-4567"
emails = re.findall(r'[\w._%+-]+@[\w.-]+\.[a-zA-Z]{2,}', text)
phones = re.findall(r'\d{3}-\d{4}', text)基本图像操作
from PIL import Image, ImageFilter, ImageDraw
img = Image.open('example.jpg')
print(f"大小: {img.size}, 格式: {img.format}")图像处理
resized = img.resize((300, 200))
rotated = img.rotate(45)
blurred = img.filter(ImageFilter.BLUR)
cropped = img.crop((100, 100, 400, 400)) # (left, top, right, bottom)绘图与保存
draw = ImageDraw.Draw(img)
draw.rectangle((50, 50, 150, 150), outline="red")
draw.text((10, 10), "Hello", fill="white")
# 保存图像
img.save('modified.jpg', quality=95)环境变量操作
import os
from dotenv import load_dotenv
load_dotenv() # 加载.env文件
api_key = os.getenv('API_KEY', '默认值')
os.environ['DEBUG'] = 'True' # 设置环境变量命令行参数
import argparse
parser = argparse.ArgumentParser(description='示例程序')
parser.add_argument('filename', help='输入文件')
parser.add_argument('-v', '--verbose', action='store_true')
args = parser.parse_args()子进程管理
import subprocess
result = subprocess.run(['ls', '-l'], capture_output=True, text=True)
print(result.stdout)单元测试
import unittest
def add(a, b): return a + b
class TestMath(unittest.TestCase):
def test_add(self):
self.assertEqual(add(1, 2), 3)
self.assertEqual(add(-1, 1), 0)
def test_add_fail(self):
self.assertNotEqual(add(1, 1), 3)性能测量
import time, timeit
def measure():
start = time.time()
result = sum(range(1000000))
print(f"耗时: {time.time() - start}秒")
return result迭代工具
from itertools import cycle, chain, islice
colors = cycle(['红', '绿', '蓝']) # 无限循环
print(next(colors), next(colors)) # 红 绿
combined = chain([1, 2], [3, 4]) # 连接多个可迭代对象
first_5 = islice(fibonacci(100), 5) # 切片迭代器创建 DataFrame
import pandas as pd
import numpy as np
data = {
'Name': ['Alice', 'Bob', 'Charlie'],
'Age': [25, 30, 35],
'City': ['北京', '上海', '广州']
}
df = pd.DataFrame(data)
df = pd.DataFrame(data)数据选择与过滤
names = df['Name'] # 选择单列
subset = df[['Name', 'Age']] # 选择多列
young = df[df['Age'] < 30] # 条件过滤数据分析
print(df.describe()) # 统计摘要
grouped = df.groupby('City').mean() # 分组统计函数缓存提高性能
from functools import lru_cache
@lru_cache(maxsize=128)
def fibonacci(n):
if n <= 1: return n
return fibonacci(n-1) + fibonacci(n-2)命名元组
from collections import namedtuple
Point = namedtuple('Point', ['x', 'y'])
p = Point(3, 4)
print(p.x, p.y) # 通过名称访问元素枚举类型
from enum import Enum, auto
class Color(Enum):
RED = 1
GREEN = 2
BLUE = auto() # 自动赋值数据类
from dataclasses import dataclass
@dataclass
class Product:
name: str
price: float
quantity: int = 0
def total_cost(self) -> float:
return self.price * self.quantityBase64 编码
import base64
encoded = base64.b64encode("Hello".encode())
decoded = base64.b64decode(encoded).decode()装饰器
import time
def timer(func):
def wrapper(*args, **kwargs):
start = time.time()
result = func(*args, **kwargs)
print(f"耗时: {time.time() - start}秒")
return result
return wrapperLambda 表达式
add = lambda x, y: x + y
sorted_items = sorted(items, key=lambda x: x[1])参数解包
def add(a, b, c): return a + b + c
values = [1, 2, 3]
print(add(*values)) # 解包列表
params = {'a': 1, 'b': 2, 'c': 3}
print(add(**params)) # 解包字典CSV 处理
import csv
with open('data.csv', 'w', newline='') as f:
writer = csv.writer(f)
writer.writerows([['Name', 'Age'], ['Alice', 25]])
with open('data.csv', 'r') as f:
reader = csv.reader(f)
for row in reader:
print(row)XML 处理
import xml.etree.ElementTree as ET
xml_str = '<root><item id="1">值</item></root>'
root = ET.fromstring(xml_str)
value = root.find('item').textHTTP 请求
import requests
response = requests.get('https://api.example.com/data')
if response.status_code == 200:
data = response.json()解析网页
from bs4 import BeautifulSoup
html = requests.get('https://example.com').text
soup = BeautifulSoup(html, 'html.parser')
title = soup.title.text
links = soup.find_all('a')属性装饰器
class Temperature:
def __init__(self, celsius):
self._celsius = celsius
@property
def celsius(self):
return self._celsius
@property
def fahrenheit(self):
return self._celsius * 9/5 + 32魔术方法
class Vector:
def __init__(self, x, y):
self.x, self.y = x, y
def __add__(self, other):
return Vector(self.x + other.x, self.y + other.y)
def __str__(self):
return f"Vector({self.x}, {self.y})"生成器函数
def fibonacci(n):
a, b = 0, 1
for i in range(n):
yield a
a, b = b, a + b生成器表达式
squares = (x**2 for x in range(10)) # 比列表推导省内存获取和格式化当前时间
from datetime import datetime, timedelta
now = datetime.now()
formatted = now.strftime("%Y-%m-%d %H:%M:%S")
print(f"当前时间: {formatted}")日期计算
tomorrow = now + timedelta(days=1)
last_week = now - timedelta(weeks=1)
time_diff = tomorrow - now # 计算时间差解析日期字符串
date_str = "2023-01-15"
date_obj = datetime.strptime(date_str, "%Y-%m-%d")JSON 处理
import json
data = {'name': 'Alice', 'age': 30}
json_str = json.dumps(data, indent=2) # 转为JSON
parsed = json.loads(json_str) # 解析JSONURL 解析与构建
from urllib.parse import urlparse, urlencode
parsed_url = urlparse("https://example.com/path")
params = {"name": "张三", "age": 30}
query = urlencode(params)异常处理
try:
result = 10 / 0 # 会引发ZeroDivisionError
except ZeroDivisionError as e:
print(f"捕获到错误: {e}")
except Exception as e:
print(f"捕获其他错误: {e}")
finally:
print("始终执行的代码")日志记录
import logging
logging.basicConfig(
level=logging.INFO,
format='%(asctime)s - %(levelname)s - %(message)s',
filename='app.log'
)
logging.info('程序启动')
logging.warning('警告信息')
logging.error('错误信息')多线程
import threading
def task(name):
print(f"线程{name}运行中")
threads = [threading.Thread(target=task, args=(i,)) for i in range(3)]
for t in threads:
t.start()异步编程
import asyncio
async def say_hello(delay, name):
await asyncio.sleep(delay)
print(f"Hello, {name}")
async def main():
await asyncio.gather(
say_hello(1, "Alice"),
say_hello(2, "Bob")
)
# asyncio.run(main()) # Python 3.7+连接和创建表
import sqlite3
# 连接数据库
conn = sqlite3.connect('example.db')
cursor = conn.cursor()
# 创建表
cursor.execute('''
CREATE TABLE IF NOT EXISTS users (
id INTEGER PRIMARY KEY,
name TEXT,
age INTEGER
)''')数据库操作
# 插入数据
cursor.execute("INSERT INTO users VALUES (?, ?, ?)", (1, 'Alice', 25))
conn.commit()
# 查询数据
cursor.execute("SELECT * FROM users WHERE age > ?", (20,))
for row in cursor.fetchall():
print(row)
conn.close()基本类定义
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def greet(self):
return f"你好，我是{self.name}"
