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I recently installed Python 2.7.3 on a CentOS machine by compiling from source. Python 2.7.3 is installed at /opt/python2.7 and when I installed it I just changed /usr/bin/python to point to the new version. This apparently is wrong though because when I did it it broke yum. I would get the following.

There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   No module named yum

Please install a package which provides this module, or
verify that the module is installed correctly.

It's possible that the above module doesn't match the
current version of Python, which is:
2.7.3 (default, May 15 2012, 17:45:42) 
[GCC 4.4.4 20100726 (Red Hat 4.4.4-13)]

If you cannot solve this problem yourself, please go to 
the yum faq at:
  http://yum.baseurl.org/wiki/Faq

I changed /usr/bin/python to point back to the python 2.6.6 but now 2.6.6 is the default version of python. Any idea how to fix this?

tbeauvais
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10 Answers10

145

I have written a quick guide on how to install the latest versions of Python 2 and Python 3 on CentOS 6 and CentOS 7. It currently covers Python 2.7.13 and Python 3.6.0:

# Start by making sure your system is up-to-date:
yum update
# Compilers and related tools:
yum groupinstall -y "development tools"
# Libraries needed during compilation to enable all features of Python:
yum install -y zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel expat-devel
# If you are on a clean "minimal" install of CentOS you also need the wget tool:
yum install -y wget

The next steps depend on the version of Python you're installing.

For Python 2.7.14:

wget http://python.org/ftp/python/2.7.14/Python-2.7.14.tar.xz
tar xf Python-2.7.14.tar.xz
cd Python-2.7.14
./configure --prefix=/usr/local --enable-unicode=ucs4 --enable-shared LDFLAGS="-Wl,-rpath /usr/local/lib"
make && make altinstall

# Strip the Python 2.7 binary:
strip /usr/local/lib/libpython2.7.so.1.0

For Python 3.6.3:

wget http://python.org/ftp/python/3.6.3/Python-3.6.3.tar.xz
tar xf Python-3.6.3.tar.xz
cd Python-3.6.3
./configure --prefix=/usr/local --enable-shared LDFLAGS="-Wl,-rpath /usr/local/lib"
make && make altinstall

# Strip the Python 3.6 binary:
strip /usr/local/lib/libpython3.6m.so.1.0

To install Pip:

# First get the script:
wget https://bootstrap.pypa.io/get-pip.py

# Then execute it using Python 2.7 and/or Python 3.6:
python2.7 get-pip.py
python3.6 get-pip.py

# With pip installed you can now do things like this:
pip2.7 install [packagename]
pip2.7 install --upgrade [packagename]
pip2.7 uninstall [packagename]

You are not supposed to change the system version of Python because it will break the system (as you found out). Installing other versions works fine as long as you leave the original system version alone. This can be accomplished by using a custom prefix (for example /usr/local) when running configure, and using make altinstall (instead of the normal make install) when installing your build of Python.

Having multiple versions of Python available is usually not a big problem as long as you remember to type the full name including the version number (for example "python2.7" or "pip2.7"). If you do all your Python work from a virtualenv the versioning is handled for you, so make sure you install and use virtualenv!

miken32
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Daniel Eriksson
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  • very nice writup = thank you very much. I would assume that python3 would be a similar set of steps correct? no major differences right? – Ryan Guill Feb 11 '13 at 16:12
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    I have now rewritten the tutorial linked in my answer so that it covers both Python 2.7.3 and Python 3.3.0 properly. I also updated the contents with better information and I expanded the section about virtualenv. – Daniel Eriksson Feb 21 '13 at 03:11
  • Thanks a lot for all the upvotes, they are very much appreciated! – Daniel Eriksson Feb 21 '13 at 03:11
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    I made an install script in bash that used this guide, thanks. Feel free to put it up on your website if you like it! https://gist.github.com/timss/5122008 – timss Apr 10 '13 at 22:28
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    Brilliant, but you might want to update it to install 2.7.4 instead. – Daniel Eriksson Apr 11 '13 at 22:57
  • @DanielEriksson Thanks, I wasn't aware of the 2.7.4 release. Easy to switch version though, it's nto really that version specific. – timss Apr 14 '13 at 01:01
  • redhat 6.4 bundles python27 in it as far as I used it last time... why py2.6 still even exists..? everybody migrates to python3 quite actively already. py2.6 is dead! – holms Oct 12 '13 at 00:57
  • Yes, I'm aware. I really should update/rewrite the post. Thanks for the nudge! – Daniel Eriksson Oct 15 '13 at 21:22
  • Thank you for your guide. When I try /usr/local/bin/python3.3 and >>> import pymysql I have ImportError: No module named 'pymysql'. If I invoke python as $ python (2.6 version) it can import this module. I wonder why Python 3 does not see it... – Evgeny Tryastsin Dec 09 '13 at 08:33
  • When you install a Python package it is installed for the specific version of Python used during installation. So you need to install pymysql for 3.3 also. – Daniel Eriksson Dec 10 '13 at 16:15
  • I followed some dude's hacked up instructions, but this probably would have been a better idea. (http://www.lecloud.net/post/61401763496/install-update-to-python-2-7-and-latest-pip-on-ec2) – cbmanica Dec 18 '13 at 09:09
  • I've updated the guide with the latest versions of Python (2.7.6 and 3.3.4), plus info about compiling as a shared library, plus Unicode UTF-32 support, plus more libraries, plus setuptools instead of distribute, plus virtualenv and pyvenv, ... – Daniel Eriksson Feb 18 '14 at 00:05
  • Just used your guide on RHEL6 and it worked flawlessly. Thank you very much Daniel! – Barmaley Sep 19 '14 at 21:00
  • I just updated the guide (and moved it to a new domain) with info about Python 2.7.13 and Python 3.6.0. I also simplified the instructions a bit and added info about using get-pip.py to install pip, setuptools and wheel. – Daniel Eriksson Feb 07 '17 at 09:32
  • @DanielEriksson i have used your article to install the python 2.7.13 along with tthe 2.6.6 in CentOS. But when i install pip it gives the error . python2.7 : command not found. any idea? – tech_geek Jun 16 '17 at 06:35
  • @adeel Do you get the error message when you try to run the get-pip.py script, or later when you try to use the newly installed pip? Are you sure you have the location where you installed python2.7 (/usr/local/bin if you followed the guide) in your PATH? – Daniel Eriksson Jul 04 '17 at 11:38
  • @DanielEriksson its been 20 days lol . anyways it was saying that python2.7 not found. – tech_geek Jul 04 '17 at 11:52
  • by banging my head for almost 5 days i switched to the digital ocean server. I called godaddy they say they have no support of django in centos vps but you can do it own yourseld – tech_geek Jul 04 '17 at 11:53
  • this is great, but how would you surpass yum install dependency issue for it `python 27(alternatives)` and `python27(dist-packages), when i just installed python27, and still persists on my amazonlinux(has happened on several old, when yum updating from a 2013 kernel ugh, i know. – blamb Apr 17 '19 at 02:54
  • I think if you spawn a clone of your broken instance using AWS EC2 then you can immediately enable /etc/yum.conf to cache rpm. Force some sort of install of python26 or python27 used by yum backup all rpm and bring them to broken instance. I think it should work but require some patience and to install each rpm in the correct order. What amazon is going to do when Python 2.7 is supposed to reach end of life on December 31 2019... They should allow yum to work with Python 3 sooner than later!! – Thomas J Younsi Aug 15 '19 at 00:54
  • for Python 2.7.x installation, `LDFLAGS="-Wl,-rpath /usr/local/lib"` is very very important, It saved my time, thanks – jk2K Apr 21 '20 at 09:53
  • 1) sudo yum groupinstall -y "development tools" has thrown following error Warning: Group development does not have any packages to install. Maybe run: yum groups mark install (see man yum) No packages in any requested group available to install or update 2) this is working yum -y groupinstall base "Development tools" --setopt=group_package_types=mandatory,default,optional – Tech User Nov 20 '20 at 06:48
  • /usr/bin/install: cannot create regular file ‘/usr/local/bin/python3.8’: Permission denied – Sunil Garg Mar 31 '21 at 14:54
14
vim `which yum`
modify #/usr/bin/python to #/usr/bin/python2.4
Alfe
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moven
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    can you explain your answer? – ejectamenta Jun 25 '16 at 19:57
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    This is the correct answer, rather than lot of article insist to change the default `python` version in the system.. that didn't works for me.. ! – Haridas N Dec 29 '16 at 06:28
  • Let's break the system by replacing Python, and then fix it by breaking yum? Not good advice. – miken32 Jan 04 '17 at 23:39
  • It's not really breaking yum, but I agree it's a risky solution. The main issue is that it's not clear what else you might break *other than* yum, and you might not immediately remember to look at the python version upgrade as a possible cause of future problems. This answer also doesn't explain what else it's recommending to do at all. – TheAtomicOption Nov 22 '17 at 18:01
  • Had to do the same change on `/usr/libexec/urlgrabber-ext-down`, after that it worked – bubbassauro Nov 09 '21 at 14:03
5

Put /opt/python2.7/bin in your PATH environment variable in front of /usr/bin...or just get used to typing python2.7.

larsks
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2

pythonz, an active fork of pythonbrew, makes this a breeze. You can install a version with:

# pythonz install 2.7.3

Then set up a symlink with:

# ln -s /usr/local/pythonz/pythons/CPython-2.7.3/bin/python2.7 /usr/local/bin/python2.7
# python2.7 --version
Python 2.7.3
Boden Garman
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1
ln -s /usr/local/bin/python2.7 /usr/bin/python
Gank
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0

Alright so for me, the error being fixed is when there are different versions of python installed and yum can't find a certain .so file and throws an exception.
yum wants 2.7.5 according to the error.

which python gives me /usr/bin/python
python --version gives me 2.7.5

The fix for me was append /lib64 to the LD_LIBRARY_PATH environment variable. The relevant content is /lib64/python2.7 and /lib64/python3.6.

export LD_LIBRARY_PATH=/lib64:$LD_LIBRARY_PATH

Fixed the yum error for me with multiple python versions installed.

Christopher Hoffman
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0

Daniel's answer is probably the most ideal one as it doesn't involve changing OS files. However, I found myself in a situation where I needed a 3rd party program which invoked python by calling usr/bin/python, but required Python 2.7.16, while the default Python was 2.7.5. That meant I had to make usr/bin/python point to a Python version of 2.7.16 version, which meant that yum wouldn't work.

What I ended up doing is editing the file /usr/bin/yum and replacing the shebang there to use to the system default Python (in my case, that meant changing #! /usr/bin/python to #! /usr/bin/python2). However, after that running yum gave me an error:

ImportError: No module named urlgrabber.grabber

I solved that by replacing the shebang in /usr/libexec/urlgrabber-ext-down the same way as in /usr/bin/yum. I.e., #! /usr/bin/python to #! /usr/bin/python2. After that yum worked.

This is a hack and should be used with care. As mentioned in other comments, modifying OS files should be last resort only.

asherbret
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-1

I recommend, instead, updating the path in the associated script(s) (such as /usr/bin/yum) to point at your previous Python as the interpreter.

Ideally, you want to upgrade yum and its associated scripts so that they are supported by the default Python installed.

If that is not possible, the above is entirely workable and tested.

Change:

#!/usr/bin/python

to whatever the path is of your old version until you can make the above yum improvement.

Cases where you couldn't do the above are if you have an isolated machine, don't have the time to upgrade rpm manually or can't connect temporarily or permanently to a standard yum repository.

j0k
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Stuart Cracraft
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    I would very much recommend to do it the other way round: Change the interpreter line in the *new* scripts to point to the *new* Python version. Don't mess with OS scripts. –  Sep 21 '12 at 08:30
  • Interestingly, the other answer of @moven up there got +6 for pretty much the same approach. – Alfe Aug 06 '15 at 09:39
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If you want to try out rpm packages, you can install binary packages based on the newest Fedora rpms, but recompiled for RHEL6/CentOS6/ScientificLinux-6 on:

http://www.jur-linux.org/download/el-updates/6/

best regards,

Florian La Roche

FlorianLa Roche
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I read a piece with a comment that states the following commands can be run now. I have not tested myself so be careful.

$ yum install -y epel-release
$ yum install -y python36
dps
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