Installing Python on Linux without disrupting existing one

Python is important package that comes installed on Linux systems. Corrupting the pre-installed version makes many of the packages non-usable. I could not yum after the pre-installed version of Python was corrupt.

Here is how you can install a version of Python on Linux operating system, keeping the pre-installed one safe. Here, we use CentOS 6.4 version, which is a pretty old release.

Issues solved by this document

pip is an important module you need while working on Python. Following are the errors I have faced while trying to install pip module and this document helps you in solving them too:

• zipimport.ZipImportError: can't decompress data; zlib not available

  [root@localhost tmp]# python2.7 get-pip.py 
  Traceback (most recent call last):
    File "get-pip.py", line 20061, in 
      main()
    File "get-pip.py", line 194, in main
      bootstrap(tmpdir=tmpdir)
    File "get-pip.py", line 82, in bootstrap
      import pip
  zipimport.ZipImportError: can't decompress 
  data; zlib not available
  

  
  

• There was a problem confirming the ssl certificate: Can't connect to HTTPS URL because the SSL module is not available.

  [root@localhost tmp]# python2.7 get-pip.py 
  pip is configured with locations that require TLS/SSL, 
  however the ssl module in Python is not available.
  Collecting pip
    Could not fetch URL https://pypi.python.org/simple/p
  ip/: There was a problem confirming the ssl certificat
  e: Can't connect to HTTPS URL because the SSL module i
  s not available. - skipping
    Could not find a version that satisfies the requirem
  ent pip (from versions: )
  No matching distribution found for pip
  [root@localhost tmp]#
  

  

Verify the current version

You may use python --version command on the terminal to find the current version.

Installing a different version

1. You may download a version you would need to install from Python Download. By default, Python comes as tarball for Linux.
2. Once you have the tarball downloaded, copy it to a location where we extract and do the installation. Here, I copied the 2.7.12 version to /tmp. Use the version which is available for your platform and remember to use the commands accordingly.
3. Extract tarball and change directory to the extracted folder.

   tar xvf Python-2.7.12.tar.xz
   cd Python-2.7.12

4. Install required Linux packages. gcc is a utility for compiling and installing Python from source, zlib-devel and openssl-devel are required to avoid errors while installing pip module at a later stage. You would need to be root or a sudoer to install these packages:

   yum install gcc
   yum install zlib-devel
   yum install openssl-devel

5. Run configure with option to export shared libraries. This is necessary if you would need to use pyinstaller module.

   ./configure --enable-shared

6. Generate the build:

   make

7. Install Python without replacing the existing version. Using altinstall option will help you to use the new installation with version suffix during execution. e.g. python2.7 --version:
   

   make altinstall

8. Make a link to Python library path:

• On 32 bit OS

  ln -s /usr/local/lib/libpython2.7.so.1.0 /usr/lib/libpython2.7.so.1.0

• On 64 bit OS

   ln -s /usr/local/lib/libpython2.7.so.1.0 /usr/lib64/libpython2.7.so.1.0

 Installing pip module

Here is how you may get pip for the Python version you have just installed:

1. Running get-pip.py is a better way to install pip. get-pip.py file is available at pip module listing.
2. Run get-pip.py with the version of Python you have installed. For example:

   python2.7 get-pip.py

   This installs a pip utility which you can use with suffix. e.g. pip2.7 install pyinstaller