(pyasn1 0.1.6 (/usr/lib/python2.7/site-packages),

ubuntu14.04下安装爬虫工具scrapy

scrapy是目前准备要学习的爬虫框架，其在ubuntu14.04下的安装过程如下：
ubuntu14.04下默认安装了2.7的python以及setuptools，若未安装，可通过下面指令安装：

sudo apt-get install pythonsudo apt-get install python-setuptools

然后安装Twisted：

sudo apt-get install python-twisted

然后是Scrapy：

sudo apt-get install python-scrapy

安装完成后，如果直接键入scrapy启动的话会报类似如下错误：

File "/usr/local/bin/scrapy", line 5, in <module>
from pkg_resources import load_entry_point

......

pkg_resources.ContextualVersionConflict: (pyasn1 0.1.7 (/usr/lib/python2.7/dist-packages), Requirement.parse('pyasn1>=0.1.8'), set(['pyasn1-modules']))

按提示是个版本依赖的错误。
此时先安装pip：

sudo apt-get install python-pip

升级pip：

sudo pip install --upgrade pip

然后对提示的pyasn1升级：

sudo pip install --upgrade pyasn1

再启动scrapy就可以成功了：

Scrapy 1.0.3 - no active project

Usage:
scrapy <command> [options] [args]

Available commands:
bench         Run quick benchmark test
commands
fetch         Fetch a URL using the Scrapy downloader
runspider     Run a self-contained spider (without creating a project)
settings      Get settings values
shell         Interactive scraping console
startproject  Create new project
version       Print Scrapy version
view          Open URL in browser, as seen by Scrapy

[ more ]      More commands available when run from project directory

Use "scrapy <command> -h" to see more info about a command