2019-04-08 临时笔记

1. bugs and fixing:

1. pip3 ImportError: cannot import name 'main':
# sudo python3 -m pip uninstall pip && sudo apt install python3-pip --reinstall

2.Failed to start mongod.service: Unit mongod.service not found
#　这个服务的名字是　mongodb, 不是mongod
# sudo service mongodb status[start | stop]

3. mongodb 启动错误：
# Loaded: masked (Reason: Unit mongodb.service is masked.)
解决: sudo systemctl unmask mongodb
参考：https://askubuntu.com/questions/919108/error-unit-mongodb-service-is-masked-when-starting-mongodb

2. 使用 scrapy:

### scrapy steps:
1. startproject         # init
2. targetSpider.py      # make it run
3. items.py             # define items
4. pipeline.py          # store to database
5. settings.py          # enable pipeline, change user-agent

tools:
1. chrome extension: css selectorGadget 
2. pip3 install scrapy-user-agent  
3. pip3 install scrapy-proxy-pool