Background briefing on tools

It's important to consider each major release of Python as an add-on and not a replacement. Any release of Python 2 should be left in place. Most field agents will have several side-by-side versions of Python on their computers. The following are the two common scenarios:

We have to distinguish between the major, minor, and micro versions of Python. Python 3.4.3 and 3.4.2 have the same minor version (3.4). We can replace the micro version 3.4.2 with 3.4.3 without a second thought; they're always compatible with each other. However, we don't treat the minor versions quite so casually. We often want to leave 3.3 in place.

Generally, we do a field upgrade as shown in the following:

At this point, we should be able to confirm that our basic toolset works. Linux and Mac OS agents can use the following command:

MacBookPro-SLott:Code slott$ python3.4

This should confirm that we've downloaded and installed Python and made it a part of our OS settings. The greeting will show which micro version of Python 3.4 have we installed.

For Windows, the command's name is usually just python. It would look similar to the following:

C:\> python

The Mac OS X interaction should include the version; it will look similar to the following code:

MacBookPro-SLott:NavTools-1.2 slott$ python3.4
Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb 23 2015, 02:52:03) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.version_info
sys.version_info(major=3, minor=4, micro=3, releaselevel='final', serial=0)

We've entered the python3.4 command. This shows us that things are working very nicely. We have Python 3.4.3 successfully installed.

We don't want to make a habit of using the python or python3 commands in order to run Python from the command line. These names are too generic and we could accidentally use Python 3.3 or Python 3.5, depending on what we have installed. We need to be intentional about using Python3.4.

The first time that we try to use pip3.4, we may see an interaction as shown in the following:

MacBookPro-SLott:Code slott$ pip3.4 install anything
You are using pip version 6.0.8, however version 7.0.3 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

The version numbers may be slightly different; this is not too surprising. The packaged version of pip isn't always the latest and greatest version. Once we've installed the Python package, we can upgrade pip3.4 to the recent release. We'll use pip to upgrade itself.

It looks similar to the following code:

MacBookPro-SLott:Code slott$ pip3.4 install --upgrade pip
You are using pip version 6.0.8, however version 7.0.3 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
Collecting pip from https://pypi.python.org/packages/py2.py3/p/pip/pip-7.0.3-py2.py3-none-any.whl#md5=6950e1d775fea7ea50af690f72589dbd
  Downloading pip-7.0.3-py2.py3-none-any.whl (1.1MB)
    100% |################################| 1.1MB 398kB/s 
Installing collected packages: pip
  Found existing installation: pip 6.0.8
    Uninstalling pip-6.0.8:
      Successfully uninstalled pip-6.0.8

Successfully installed pip-7.0.3

We've run the pip installer to upgrade pip. We're shown some details about the files that are downloaded and new is version installed. We were able to do this with a simple pip3.4 under Mac OS X.

Some packages will require system privileges that are available via the sudo command. While it's true that a few packages don't require system privileges, it's easy to assume that privileges are always required. For Windows, of course, we don't use sudo at all.

On Mac OS X, we'll often need to use sudo -H instead of simply using sudo. This option will make sure that the proper HOME environment variable is used to manage a cache directory.

Note that your actual results may differ from this example, depending on how out-of-date your copy of pip turns out to be. This pip install --upgrade pip is a pretty frequent operation as the features advance.