Python 随手记

1. 拼接路径时，python 用

os.path.join("a","b","c","d")

会根据操作系统的不同拼接出正确的路径。

2. 多行字符串格式化。

例子：

raws=""" 
The first string is %s
The second string is %s
The last string is %s
"""%('1','2','3')

记得格式化"""%('1','2','3')这里不要有空格

3. requests获取网页响应时间用法：单位是微秒

import requests
r = requests.get("http://www.baidu.com")
r.elapsed.microseconds

4. pymongo 显示报错信息cursor id is not valid at server

db.collection.find() 返回的是一个cursor，而不是所有数据，
比较好的解决办法是：控制batch_size的数量，让其在10分能跑完，避免cursor超时。

for doc in db.collection.find().batch_size(50):

5. python 快速生成包含同一元素的列表方法：

port = 22
portList = [port] * 10
#生成结果[22,22,22,22,22,22,22,22,22,22]

6. requests的使用

#忽略证书错误
requests.get('https://baidu.com', verify=False)

#使用代理获取百度首页
import requests
 headers = {
          "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"
}
## 定义代理的字典
proxies = {
          # "http":"http://114.18.52.4:6666"
          # "https":"https://114.19.30.126:8888"
          # "http":"http://username:password@ip:端口号" #带账号密码的代理
          #"https": "https://username:password@ip:端口号"
          "http": "http://120.28.18.93:8001"
}
 ## 使用代理给服务器发送请求
response = requests.get("https://www.baidu.com", proxies=proxies, headers=headers)
## 获取状态
print(response.status_code)
print(response.content.decode())

7. pymongo 把结果json化

#数据库连接文件dbc.py
import pymongo, sys, traceback

MONGODB_CONFIG = {
    'host': '192.168.1.1',
    'port': 27017,
    'db_name': 'test',
    'username': 'test',
    'password': 'test'
}


class MongoConn(object):
    def __init__(self):
        try:
            self.conn = pymongo.MongoClient(MONGODB_CONFIG['host'], MONGODB_CONFIG['port'])
            self.db = self.conn[MONGODB_CONFIG['db_name']]
            self.username = MONGODB_CONFIG['username']
            self.password = MONGODB_CONFIG['password']
            if self.username and self.password:
                self.connect = self.db.authenticate(self.username, self.password)
            else:
                self.connect = True
        except Exception:
            print(traceback.format_exc())
            print("Connect db Fail!!")
            sys.exit(1)

#结果按json格式输出
from dbc import MongoConn
from bson.objectid import ObjectId
from bson import json_util as jsonb
md = MongoConn()
result = md.db['sshDb'].find({"tryPassWord": {"$nin": [password]}}, {'ip': 1, "_id": 0}).batch_size(10)
res = json.loads(jsonb.dumps(result))
print(res)

8. 打开大文件如何减少内存占用,错误提示MemoryError。

#文本文件用直接迭代文件
with open('password.txt', 'r', 'utf-8', buffering=True)as lines:
    for line in lines:
        print(line)
#或者
with open('password.txt', 'rb', 'utf-8', buffering=True) as f:
    while True:
        line = f.readline()
        if line:    
            print(line)
        else:
            break

#二进制文件
with open('password.txt', 'rb') as f:
    while True:
        buf = f.read(1024)
        if buf:    
            sha1Obj.update(buf)
        else:
            break

小端转大端(大端为适合人类阅读顺序)

#适用于python2
"6fe28c".decode('hex')[::-1].encode('hex_codec')
# output: '8ce26f'

jupyter notebook打开命令

#cmd 下运行
jupyter notebook

conda常用命令

#创建环境，py27是环境别名，2.7是python的版本
conda create -n py27 python=2.7
#查看所有安装的环境
conda env list
#激活环境
conda activate py27

在当前目录安装lxml依赖包

pip install lxml -t .