一些Python3的代码比较耗时，想挂到VPS上跑，VPS 的 CentOS 默认只提供了Python2，所以需要升级到Python3。

查看系统和python版本：

查看Linux系统类型和版本

[root@** ~]# head -n 1 /etc/issue
CentOS release 6.7 (Final)

查看Python版本

[root@** ~]# python
Python 2.6.6 (r266:84292, Jul 23 2015, 15:22:56)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-11)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()

查完了记得退出Python环境。（我干了件蠢事，在python下输入 wget 结果提示我语法错误，半天才反应过来。）

或者直接用：

[root@** ~]# python -V
Python 2.6.6 

下载Python安装包并安装：

打开python官网ftp目录

https://www.python.org/ftp/python/

，挑一个的3.x版本。

下载安装包

wget http://www.python.org/ftp/python/3.5.2/Python-3.5.2.tgz

…

Saving to: “Python-3.5.2.tgz”

100%[======================================>] 20,566,643 11.5M/s in 1.7s

2016-10-08 01:22:56 (11.5 MB/s) – “Python-3.5.2.tgz” saved [20566643/20566643]

解压安装包

tar -zxvf Python-3.5.2.tgz

…

Python-3.5.2/Include/metagrammar.h

Python-3.5.2/Include/classobject.h

Python-3.5.2/Include/patchlevel.h

Python-3.5.2/Include/sysmodule.h

Python-3.5.2/Include/dynamic_annotations.h

Python-3.5.2/Include/tupleobject.h

进入解压目录

cd Python-3.5.2

创建安装目录

mkdir /usr/local/python3.5

编译安装第一步：配置

./configure --prefix=/usr/local/python3.5

安装gcc

yum -y install gcc

./configure --prefix=/usr/local/python3.5

make

…

Python build finished successfully!

The necessary bits to build these optional modules were not found:

_bz2 _curses _curses_panel

_dbm _gdbm _lzma

_sqlite3 _ssl _tkinter

readline zlib

To find the necessary bits, look in setup.py in detect_modules() for the module’s name.

running build_scripts

creating build/scripts-3.5

copying and adjusting /root/Python-3.5.2/Tools/scripts/pydoc3 -> build/scripts-3.5

copying and adjusting /root/Python-3.5.2/Tools/scripts/idle3 -> build/scripts-3.5

…

# Substitution happens here, as the completely-expanded BINDIR

# is not available in configure

sed -e “s,@EXENAME@,/usr/local/python3.5/bin/python3.5m,” < ./Misc/python-config.in >python-config.py

# Replace makefile compat. variable references with shell script compat. ones; ->

sed -e ‘s,\$(\([A-Za-z0-9_]*\)),\$\{\1\},g’ < Misc/python-config.sh >python-config

…

时间可能长了点，花了几分钟，提示建立成功。

看到中间那一大片not found的模块了么，一开始我忽略了，导致后面出现了一些问题，我后面说。

至于两行sed提示，参照其他博客的经验，直接复制运行了一下这两条文本处理指令：

sed -e "s,@EXENAME@,/usr/local/python3.5/bin/python3.5m," < ./Misc/python-config.in >python-config.py
sed -e 's,\$(\([A-Za-z0-9_]*\)),\$\{\1\},g' < Misc/python-config.sh >python-config

重新make

make

同样是successfully，一堆not found，只不过这次下面少了两行sed提示，不知道和刚才有什么不同。不过既然没提示其他问题，就接着往下装吧。

编译安装第三步：安装

make install

屏幕滚动，同样需要跑几分钟。可能是远程链接的国外VPS上安装的原因，如果是本地机器可能会快一些吧。

…

rm -f /usr/local/python3.5/share/man/man1/python3.1

(cd /usr/local/python3.5/share/man/man1; ln -s python3.5.1 python3.1)

if test “xupgrade” != “xno” ; then \

case upgrade in \

upgrade) ensurepip=”–upgrade” ;; \

install|*) ensurepip=”” ;; \

esac; \

./python -E -m ensurepip \

$ensurepip –root=/ ; \

fi

Ignoring ensurepip failure: pip 8.1.1 requires SSL/TLS

不理会pip安装的问题，先看一下Python3.5.2安装成功了没有

修改路径

备份原有python命令执行文件

mv /usr/bin/python /usr/bin/pythonbak

创建新python软连接

ln -s /usr/local/python3.5/bin/python3.5 /usr/bin/python

运行Python

python
Python 3.5.2 (default, Oct  8 2016, 02:05:39)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print('Hello World')
Hello World
>>>

提示3.5.2，用括号方式print成功，安装完成！

其他问题：

接下来解决一些之前没解决的问题。

CentOS升级Python导致yum无法使用

yun是在python2.6的支持下使用，查了一些博客，有的只是将python从2.6升到2.7，yum都会报错。

yum

File “/usr/bin/yum”, line 30

except KeyboardInterrupt, e:

^

SyntaxError: invalid syntax

所以这里我们需要改一下yum的配置文件，变更python支持路径。

vi /usr/bin/yum

将第一行的python改成python2.6即可：

1. 点击“i”进入插入修改模式；

2. “Esc”退出修改模式；

3. 冒号“:”打开控制台，输入”wq”回车，存盘退出。

#!/usr/bin/python2.6

import sys

try:

import yum

except ImportError:

print >> sys.stderr, “””\

There was a problem importing one of the Python modules

required to run yum. The error leading to this problem was:

…

再试试yum

yum

Loaded plugins: fastestmirror

You need to give some command

Usage: yum [options] COMMAND

List of Commands:

…

OK，没问题了，yum可以用了

Python升级时跳过的SSL模块的问题

之前出现过的语句

pip 8.1.1 requires SSL/TLS

我们用刚弄好的yum安装一下ssl：

yum install openssl-devel

中间询问是否下载的时候输入“y”

… libselinux-utils x86_64 2.0.94-7.el6 base 82 k openssl x86_64 1.0.1e-48.el6_8.3 updates 1.5 MTransaction Summary================================================================================Install 7 Package(s)Upgrade 4 Package(s)Total download size: 4.4 MIs this ok [y/N]: y……Dependency Updated: krb5-libs.x86_64 0:1.10.3-57.el6 libselinux.x86_64 0:2.0.94-7.el6 libselinux-utils.x86_64 0:2.0.94-7.el6 openssl.x86_64 0:1.0.1e-48.el6_8.3Complete!

全是自动运行，Complete就完成了。

同理，也可以把其他之前提示no found的东西装上，格式如下：

yum install sqlite sqlite-devel
yum install bzip2 bzip2-devel
yum install readline-devel

装完之后重新配置安装一下python

make clean && ./configure && make && sudo make install

PIP安装（只做记录）

关于pip这个东西折腾了半天，之前本以为ssl正常了，可以弄pip了。结果发现提示[忘了截图了]大概意思是缺少模块之类的。参照网上经验下载了个ez_setup.py(wget https://bootstrap.pypa.io/ez_setup.py)然后用2.6版本的python执行了一下，再输入pip还是提示有问题。我是在这之后才重新配置安装python的。

这次重装python后pip和setuptools虽然都提示安装成功了，但是pip还是用不了。其中一句错误提示是需要pip7.1

pkg_resources.VersionConflict: (pip 8.1.1 (/usr/local/python3.5/lib/python3.5/site-packages), Requirement.parse(‘pip==7.1.0’))

没怎么细看，直接去找7.1 https://pypi.python.org/pypi/pip/7.1.0 ，下载装上

wget https://pypi.python.org/packages/7e/71/3c6ece07a9a885650aa6607b0ebfdf6fc9a3ef8691c44b5e724e4eee7bf2/pip-7.1.0.tar.gz#md5=d935ee9146074b1d3f26c5f0acfd120e
tar -xzvf pip-7.1.0.tar.gz
cd pip-7.1.0
python setup.py install

然后再来一句pip，终于能用了

pip

Usage:

pip <command> [options]

Commands:

install Install packages.

uninstall Uninstall packages.

freeze Output installed packages in requirements format.

list List installed packages.

show Show information about installed packages.

search Search PyPI for packages.

wheel Build wheels from your requirements.

再查一下pip版本

pip -V

pip 7.1.0 from /usr/local/python3.5/lib/python3.5/site-packages/pip-7.1.0-py3.5.egg (python 3.5)

貌似是之前的版本装高了，能用就好。

装个requests试一下：

pip install requests

You are using pip version 7.1.0, however version 8.1.2 is available.

You should consider upgrading via the ‘pip install –upgrade pip’ command.

Collecting requests

Using cached requests-2.11.1-py2.py3-none-any.whl

Installing collected packages: requests

Successfully installed requests-2.11.1

python

Python 3.5.2 (default, Oct  9 2016, 01:20:37)

[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)] on linux

Type “help”, “copyright”, “credits” or “license” for more information.

>>> import requests

>>> requests.get(‘http://www.baidu.com’).text

‘<!DOCTYPE html>\r\n<!–STATUS OK–><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8><meta http-equiv=X-UA-Compatible …

没问题喽~先用用看

=====

有的时候pip install requests提示已安装，但是运行python3 却提示 ImportError: No module named ‘requests’，的解决方法如下：

直接安装到python3的目录中

pip install --target='/usr/lib/python3.5/' requests

或安装到要执行的py文件所在目录

pip install -t 文件运行目录 requests