安装python爬虫scrapy踩过的那些坑和编程外的思考

　　这些天应朋友的要求抓取某个论坛帖子的信息，网上搜索了一下开源的爬虫资料，看了许多对于开源爬虫的比较发现开源爬虫scrapy比较好用。但是以前一直用的java和php，对python不熟悉，于是花一天时间粗略了解了一遍python的基础知识。然后就开干了，没想到的配置一个运行环境就花了我一天时间。下面记录下安装和配置scrapy踩过的那些坑吧。

　　运行环境：CentOS 6.0 虚拟机

　　开始上来先得安装python运行环境。然而我运行了一下python命令，发现已经自带了，窃（大）喜（坑）。于是google搜索了一下安装步骤，pip install Scrapy直接安装，发现不对。少了pip，于是安装pip。再次pip install Scrapy，发现少了python-devel，于是这么来回折腾了一上午。后来下载了scrapy的源码安装，突然曝出一个需要python2.7版本，再通过python --version查看，一个2.6映入眼前；顿时千万个草泥马在心中奔腾。

　　于是查看了官方文档（http://doc.scrapy.org/en/master/intro/install.html），果然是要python2.7。没办法，只能升级python的版本了。

1、升级python

• 下载python2.7并安装

wget https://www.python.org/ftp/python/2.7.10/Python-2.7.10.tgz
tar -zxvf Python-2.7.10.tgz
cd Python-2.7.10
./configure  
make all             
make installmake clean  
make distclean  

• 检查python版本

python --version

　　发现还是2.6

• 更改python命令指向

mv /usr/bin/python /usr/bin/python2.6.6_bak
ln -s /usr/local/bin/python2.7 /usr/bin/python

• 再次检查版本

# python --version
Python 2.7.10

　　到这里，python算是升级完成了，继续安装scrapy。于是pip install scrapy，还是报错。

-bash: pip: command not found

• 安装pip

wget https://bootstrap.pypa.io/get-pip.py
python get-pip.py

　　于是pip install scrapy，还是报错

Collecting Twisted>=10.0.0 (from scrapy)
  Could not find a version that satisfies the requirement Twisted>=10.0.0 (from scrapy) (from versions: )
No matching distribution found for Twisted>=10.0.0 (from scrapy)

　　少了Twisted，于是安装Twisted

2、安装Twisted

• 下载Twisted（https://pypi.python.org/packages/source/T/Twisted/Twisted-15.2.1.tar.bz2#md5=4be066a899c714e18af1ecfcb01cfef7）
• 安装

wget https://pypi.python.org/packages/source/T/Twisted/Twisted-15.2.1.tar.bz2
tar -xjvf Twisted-15.2.1.tar.bz2
cd Twisted-15.2.1
python setup.py install

• 查看是否安装成功

python
Python 2.7.10 (default, Jun  5 2015, 17:56:24) 
[GCC 4.4.4 20100726 (Red Hat 4.4.4-13)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import twisted
>>> 

　　此时索命twisted已经安装成功。于是继续pip install scrapy，还是报错。

3、安装libxlst、libxml2和xslt-config

Collecting libxlst
  Could not find a version that satisfies the requirement libxlst (from versions: )
No matching distribution found for libxlst

Collecting libxml2
  Could not find a version that satisfies the requirement libxml2 (from versions: )
No matching distribution found for libxml2

wget http://xmlsoft.org/sources/libxslt-1.1.28.tar.gz
tar -zxvf libxslt-1.1.28.tar.gz
cd libxslt-1.1.28/
./configure
make
make install

wget ftp://xmlsoft.org/libxml2/libxml2-git-snapshot.tar.gz
tar -zxvf libxml2-git-snapshot.tar.gz
cd libxml2-2.9.2/
./configure
make
make install

 　　安装好以后继续pip install scrapy，幸运之星仍未降临

4、安装cryptography

Failed building wheel for cryptography

　　下载cryptography（https://pypi.python.org/packages/source/c/cryptography/cryptography-0.4.tar.gz）

　　安装

wget https://pypi.python.org/packages/source/c/cryptography/cryptography-0.4.tar.gz
tar -zxvf cryptography-0.4.tar.gz
cd cryptography-0.4
python setup.py build
python setup.py install

　　发现安装的时候报错：

No package 'libffi' found

　　于是下载libffi下载并安装

wget ftp://sourceware.org/pub/libffi/libffi-3.2.1.tar.gz
tar -zxvf libffi-3.2.1.tar.gz
cd libffi-3.2.1
./configure
make
make install

　　安装后发现仍然报错

Package libffi was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libffi.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libffi' found

　　于是设置：PKG_CONFIG_PATH

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:$PKG_CONFIG_PATH

　　再次安装scrapy

pip install scrapy

　　幸运女神都去哪儿了？　　

ImportError: libffi.so.6: cannot open shared object file: No such file or directory

　　于是

whereis libffi
libffi: /usr/local/lib/libffi.a /usr/local/lib/libffi.la /usr/local/lib/libffi.so

　　已经正常安装，网上搜索了一通，发现是LD_LIBRARY_PATH没设置，于是

export LD_LIBRARY_PATH=/usr/local/lib

　　于是继续安装cryptography-0.4

python setup.py build
python setup.py install

　　此时正确安装，没有报错信息了。

　　5、继续安装scrapy

pip install scrapy

　　看着提示信息：

Building wheels for collected packages: cryptography
  Running setup.py bdist_wheel for cryptography

　　在这里停了好久，在想幸运女神是不是到了。等了一会

Requirement already satisfied (use --upgrade to upgrade): zope.interface>=3.6.0 in /usr/local/lib/python2.7/site-packages/zope.interface-4.1.2-py2.7-linux-i686.egg (from Twisted>=10.0.0->scrapy)
Collecting cryptography>=0.7 (from pyOpenSSL->scrapy)
  Using cached cryptography-0.9.tar.gz
Requirement already satisfied (use --upgrade to upgrade): setuptools in /usr/local/lib/python2.7/site-packages (from zope.interface>=3.6.0->Twisted>=10.0.0->scrapy)
Requirement already satisfied (use --upgrade to upgrade): idna in /usr/local/lib/python2.7/site-packages (from cryptography>=0.7->pyOpenSSL->scrapy)
Requirement already satisfied (use --upgrade to upgrade): pyasn1 in /usr/local/lib/python2.7/site-packages (from cryptography>=0.7->pyOpenSSL->scrapy)
Requirement already satisfied (use --upgrade to upgrade): enum34 in /usr/local/lib/python2.7/site-packages (from cryptography>=0.7->pyOpenSSL->scrapy)
Requirement already satisfied (use --upgrade to upgrade): ipaddress in /usr/local/lib/python2.7/site-packages (from cryptography>=0.7->pyOpenSSL->scrapy)
Requirement already satisfied (use --upgrade to upgrade): cffi>=0.8 in /usr/local/lib/python2.7/site-packages (from cryptography>=0.7->pyOpenSSL->scrapy)
Requirement already satisfied (use --upgrade to upgrade): ordereddict in /usr/local/lib/python2.7/site-packages (from enum34->cryptography>=0.7->pyOpenSSL->scrapy)
Requirement already satisfied (use --upgrade to upgrade): pycparser in /usr/local/lib/python2.7/site-packages (from cffi>=0.8->cryptography>=0.7->pyOpenSSL->scrapy)
Building wheels for collected packages: cryptography
  Running setup.py bdist_wheel for cryptography
  Stored in directory: /root/.cache/pip/wheels/d7/64/02/7258f08eae0b9c930c04209959c9a0794b9729c2b64258117e
Successfully built cryptography
Installing collected packages: cryptography
  Found existing installation: cryptography 0.4
    Uninstalling cryptography-0.4:
      Successfully uninstalled cryptography-0.4
Successfully installed cryptography-0.9

　　显示如此的信息。看到此刻，内流马面。谢谢CCAV，感谢MTV，钓鱼岛是中国的。终于安装成功了。

6、测试scrapy

创建测试脚本

cat > myspider.py <<EOF

from scrapy import Spider, Item, Field

class Post(Item):
    title = Field()

class BlogSpider(Spider):
    name, start_urls = 'blogspider', ['http://www.cnblogs.com/rwxwsblog/']

    def parse(self, response):
        return [Post(title=e.extract()) for e in response.css("h2 a::text")]

EOF

　　测试脚本能否正常运行

scrapy runspider myspider.py

2015-06-06 20:25:16 [scrapy] INFO: Scrapy 1.0.0rc2 started (bot: scrapybot)
2015-06-06 20:25:16 [scrapy] INFO: Optional features available: ssl, http11
2015-06-06 20:25:16 [scrapy] INFO: Overridden settings: {}
2015-06-06 20:25:16 [py.warnings] WARNING: :0: UserWarning: You do not have a working installation of the service_identity module: 'No module named service_identity'.  Please install it from <https://pypi.python.org/pypi/service_identity> and make sure all of its dependencies are satisfied.  Without the service_identity module and a recent enough pyOpenSSL to support it, Twisted can perform only rudimentary TLS client hostname verification.  Many valid certificate/hostname mappings may be rejected.

2015-06-06 20:25:16 [scrapy] INFO: Enabled extensions: CloseSpider, TelnetConsole, LogStats, CoreStats, SpiderState
2015-06-06 20:25:16 [scrapy] INFO: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, MetaRefreshMiddleware, HttpCompressionMiddleware, RedirectMiddleware, CookiesMiddleware, ChunkedTransferMiddleware, DownloaderStats
2015-06-06 20:25:16 [scrapy] INFO: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2015-06-06 20:25:16 [scrapy] INFO: Enabled item pipelines: 
2015-06-06 20:25:16 [scrapy] INFO: Spider opened
2015-06-06 20:25:16 [scrapy] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2015-06-06 20:25:16 [scrapy] DEBUG: Telnet console listening on 127.0.0.1:6023
2015-06-06 20:25:17 [scrapy] DEBUG: Crawled (200) <GET http://www.cnblogs.com/rwxwsblog/> (referer: None)
2015-06-06 20:25:17 [scrapy] INFO: Closing spider (finished)
2015-06-06 20:25:17 [scrapy] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 226,
 'downloader/request_count': 1,
 'downloader/request_method_count/GET': 1,
 'downloader/response_bytes': 5383,
 'downloader/response_count': 1,
 'downloader/response_status_count/200': 1,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2015, 6, 6, 12, 25, 17, 310084),
 'log_count/DEBUG': 2,
 'log_count/INFO': 7,
 'log_count/WARNING': 1,
 'response_received_count': 1,
 'scheduler/dequeued': 1,
 'scheduler/dequeued/memory': 1,
 'scheduler/enqueued': 1,
 'scheduler/enqueued/memory': 1,
 'start_time': datetime.datetime(2015, 6, 6, 12, 25, 16, 863599)}
2015-06-06 20:25:17 [scrapy] INFO: Spider closed (finished)

　　运行正常（此时心中窃喜，^_^....）。

　　7、创建自己的scrapy项目（此时换了一个会话）

scrapy startproject tutorial

　　输出以下信息

Traceback (most recent call last):
  File "/usr/local/bin/scrapy", line 9, in <module>
    load_entry_point('Scrapy==1.0.0rc2', 'console_scripts', 'scrapy')()
  File "/usr/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 552, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2672, in load_entry_point
    return ep.load()
  File "/usr/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2345, in load
    return self.resolve()
  File "/usr/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2351, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/__init__.py", line 48, in <module>
    from scrapy.spiders import Spider
  File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/spiders/__init__.py", line 10, in <module>
    from scrapy.http import Request
  File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/http/__init__.py", line 11, in <module>
    from scrapy.http.request.form import FormRequest
  File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/http/request/form.py", line 9, in <module>
    import lxml.html
  File "/usr/local/lib/python2.7/site-packages/lxml/html/__init__.py", line 42, in <module>
    from lxml import etree
ImportError: /usr/lib/libxml2.so.2: version `LIBXML2_2.9.0' not found (required by /usr/local/lib/python2.7/site-packages/lxml/etree.so)

　　心中无数个草泥马再次狂奔。怎么又不行了？难道会变戏法？定定神看了下：ImportError: /usr/lib/libxml2.so.2: version `LIBXML2_2.9.0' not found (required by /usr/local/lib/python2.7/site-packages/lxml/etree.so)。这是那样的熟悉呀！想了想，这怎么和前面的ImportError: libffi.so.6: cannot open shared object file: No such file or directory那么类似呢？于是

　　8、添加环境变量

export LD_LIBRARY_PATH=/usr/local/lib

　　再次运行：

scrapy startproject tutorial

　　输出以下信息：

[root@bogon scrapy]# scrapy startproject tutorial
2015-06-06 20:35:43 [scrapy] INFO: Scrapy 1.0.0rc2 started (bot: scrapybot)
2015-06-06 20:35:43 [scrapy] INFO: Optional features available: ssl, http11
2015-06-06 20:35:43 [scrapy] INFO: Overridden settings: {}
New Scrapy project 'tutorial' created in:
    /root/scrapy/tutorial

You can start your first spider with:
    cd tutorial
    scrapy genspider example example.com

　　尼玛的终于成功了。由此可见，scrapy运行的时候需要LD_LIBRARY_PATH环境变量的支持。可以考虑将其加入环境变量中

vi /etc/profile

　　添加：export LD_LIBRARY_PATH=/usr/local/lib 这行（前面的PKG_CONFIG_PATH也可以考虑添加进来，export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig:$PKG_CONFIG_PATH）

　　注：安装的时候可以留意Libraries安装的路径，以libffi为例：

libtool: install: /usr/bin/install -c .libs/libffi.so.6.0.4 /usr/local/lib/../lib64/libffi.so.6.0.4
libtool: install: (cd /usr/local/lib/../lib64 && { ln -s -f libffi.so.6.0.4 libffi.so.6 || { rm -f libffi.so.6 && ln -s libffi.so.6.0.4 libffi.so.6; }; })
libtool: install: (cd /usr/local/lib/../lib64 && { ln -s -f libffi.so.6.0.4 libffi.so || { rm -f libffi.so && ln -s libffi.so.6.0.4 libffi.so; }; })
libtool: install: /usr/bin/install -c .libs/libffi.lai /usr/local/lib/../lib64/libffi.la
libtool: install: /usr/bin/install -c .libs/libffi.a /usr/local/lib/../lib64/libffi.a
libtool: install: chmod 644 /usr/local/lib/../lib64/libffi.a
libtool: install: ranlib /usr/local/lib/../lib64/libffi.a
libtool: finish: PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/www/wdlinux/mysql/bin:/root/bin:/sbin" ldconfig -n /usr/local/lib/../lib64
----------------------------------------------------------------------
Libraries have been installed in:
   /usr/local/lib/../lib64

If you ever happen to want to link against installed libraries
in a given directory, LIBDIR, you must either use libtool, and
specify the full pathname of the library, or use the `-LLIBDIR'
flag during linking and do at least one of the following:
   - add LIBDIR to the `LD_LIBRARY_PATH' environment variable
     during execution
   - add LIBDIR to the `LD_RUN_PATH' environment variable
     during linking
   - use the `-Wl,-rpath -Wl,LIBDIR' linker flag
   - have your system administrator add LIBDIR to `/etc/ld.so.conf'

See any operating system documentation about shared libraries for
more information, such as the ld(1) and ld.so(8) manual pages.
----------------------------------------------------------------------
 /bin/mkdir -p '/usr/local/share/info'
 /usr/bin/install -c -m 644 ../doc/libffi.info '/usr/local/share/info'
 install-info --info-dir='/usr/local/share/info' '/usr/local/share/info/libffi.info'
 /bin/mkdir -p '/usr/local/lib/pkgconfig'
 /usr/bin/install -c -m 644 libffi.pc '/usr/local/lib/pkgconfig'
make[3]: Leaving directory `/root/python/libffi-3.2.1/x86_64-unknown-linux-gnu'
make[2]: Leaving directory `/root/python/libffi-3.2.1/x86_64-unknown-linux-gnu'
make[1]: Leaving directory `/root/python/libffi-3.2.1/x86_64-unknown-linux-gnu'

　　这里可以知道libffi安装的路径为/usr/local/lib/../lib64，因此在引入LD_LIBRARY_PATH时应该为：export LD_LIBRARY_PATH=/usr/local/lib:/usr/local/lib64:$LD_LIBRARY_PATH，此处需要特别留意。

　　保存后检查是否存在异常：

source /etc/profile

　　开一个新的会话运行

scrapy runspider myspider.py

　　发现正常运行，可见LD_LIBRARY_PATH是生效的。至此scrapy就算正式安装成功了。

　　查看scrapy版本：运行scrapy version，看了下scrapy的版本为“Scrapy 1.0.0rc2”

9、编程外的思考(感谢阅读到此的你，我自己都有点晕了。)

• • 有没有更好的安装方式呢？我的这种安装方式是否有问题？有的话请告诉我。（很多依赖包我采用pip和easy_install都无法安装，感觉是pip配置文件配置源的问题）
  • 一定要看官方的文档，Google和百度出来的结果往往是碎片化的，不全面。这样可以少走很多弯路，减少不必要的工作量。
  • 遇到的问题要先思考，想想是什么问题再Google和百度。
  • 解决问题要形成文档，方便自己也方便别人。

　　10、参考文档

　　　　http://scrapy.org/

　　　　http://doc.scrapy.org/en/master/

　　　　http://blog.csdn.net/slvher/article/details/42346887

　　　　http://blog.csdn.net/niying/article/details/27103081

　　　　http://www.cnblogs.com/xiaoruoen/archive/2013/02/27/2933854.html