Git Reference

Git community book online:
creating:init, branch
adding and removing files::add, rm
seeing activity:log, status
basic repository operations are: push, pull, commit, checkout, clone, fetch, merge
undoing changes: reset, checkout, revert
see files in the repo:ls-files
finding stuff:grep

Some git cheat sheets:

How do I see the differences between file versions?
git diff <commit hash> <filename>

How do I go back a to version x?
Then to revert a specific file to that commit use the reset command:
git reset <commit hash> <filename>

You may need to use the --hard option if you have local modifications.
A good workflow for managaging waypoints is to use tags to cleanly mark points in your timeline. I can't quite understand your last sentence but what you may want is diverge a branch from a previous point in time. To do this, use the handy checkout command:

git checkout <commit hash>
git checkout -b <new branch name>

You can then rebase that against your mainline when you are ready to merge those changes:
git checkout <my branch>
git rebase master
git checkout master
git merge <my branch>

How do I find/look at a files history (log)?
git log <filename>

Using --stat with log will show what files changed and by how much.
git log --stat

There is also a --pretty option that provides several nicer ways of presenting the results
git log --pretty=oneline
git log --pretty=short
git log --pretty=format:'%h was %an, %ar, message: %s'

You can also use 'medium', 'full', 'fuller', 'email' or 'raw'. If those formats aren't exactly what you need, you can also create your own format with the '--pretty=format' option (see the git log docs for all the formatting options).

How do I roll back/throw away current changes?
Use checkout if you haven’t committed yet.
$ git checkout -- hello.rb
$ git checkout HEAD hello.rb,_checkout_and_revert.html

Use revert to fix committed mistakes.

You have to be careful when you say "rollback". If you used to have one version of a file in commit $A, and then later made two changes in two separate commits $B and $C (so what you are seeing is the third iteration of the file), and if you say "I want to roll back to the first one", do you really mean it?
If you want to get rid of the changes both the second and the third iteration, it is very simple:

$ git checkout $A file

and then you commit the result. The command asks "I want to check out the file from the state recorded by the commit $A".
On the other hand, what you meant is to get rid of the change the second iteration (i.e. commit $B) brought in, while keeping what commit $C did to the file, you would want to revert $B

$ git revert $B

Note that whoever created commit $B may not have been very disciplined and may have committed totally unrelated change in the same commit, and this revert may touch files other than file you see offending changes, so you may want to check the result carefully after doing so.

Disclaimer: I created the layout of this document, along with the questions I wanted answered for myself.  The answers are gleaned and lightly edited from results I found during the research process.  Quite a few answers were found on

Python Coding Standard, Metrics and Test Coverage


My motivation in seeking a coding standard, static code metrics analyzer and test coverage tool is multifaceted.  I want to know that my Python code is formatted in a way that is accepted by the community.  I want to be able to quickly check the cyclomatic complexity of code.  It is my intent to test drive my code.  Therefore, I wanted a tool which could show me and others the level of code coverage and any areas that need to be brought under test.

Note that the preferred download for all three of these tools is a .tar.gz format file.  On a Windows system you’ll need a tool like 7-zip.  All of this guidance is intended for use with Python 2.7 and PyCharm 1.5.4.  You need to add C:\Python27\ to your PATH environment variable in order to successfully install these tools.


PEP8 is a tool that provides guidance that you are following proper Python coding formatting.  Download from here:

Extract the PEP8 folder.  Using a command prompt change to the extracted PEP8 folder directory.  Run: python install There should now be a pep8.exe and in your python installations scripts directory.  You can now delete the extracted PEP8 folder.

PEP8 with PyCharm


PyCharm already has a number of features present in various tools to lint/check your source code with, but offers a way to hook up external tools. Under File > Settings is a section called IDE Settings. One of the headings here is called External Tools. Select this heading and then press the Add... button on the right hand pane to configure a new external tool.

In the Edit Tool window that now appeared fill in a name, e.g. PEP8 and a group name Lint and add a description. Next point the Program to the location of the pep8.exe executable, e.g. C:\Python27\Scripts\pep8.exe. ForParameters you need to use $FilePath$ and Working directory should be same as the Python scripts directory. Once done, you can close it by pressing the OK button.

Now add a filter to the external tool to get click-and-go-to behavior


See for how to add filters.

use this for the spec: $FILE_PATH$:$LINE$:$COLUMN$:.*


Select a file either in the navigator or editor panes.

Then from menu can go to Tools > Lint > PEP8

You'll also have links you can click on for the PEP8 output.

Following my initial installation notes on a second machine I was getting a urllib.parse error from PEP8.exe, "no module named parse" Seemed like this problem is related to distribute. Pulled down the latest from Nope, wouldn't install. Looking like issue with C:\python27\lib\  Web pointed me to reinstall setuptools  Installed that… tried to install distribute again… still no go… X|  Ended up doing a python install to get distribute installed.  Now, PEP8 works!


PyMetrics is a tool for doing static code analysis.  Download it here: There is a tar.gz on SourceForge. However, the pymetrics runner does not have the .py extension which causes problems with extraction on a Windows System.

Extract your downloaded file.  Change to that directory and run python install  You can now delete the extracted folder.  Now if you look in your Python scripts directory you'll find a

Set up as an external tool in PyCharm as with PEP8.


The --nosql and --nocsv options tell the tool to not generate associated SQL insert code and suppresses the generation of a related CSV file.

Sample output from

An earlier version of the that was analyzed can be found here:

C:\Python27\python.exe C:\Python27\Scripts\pymetrics C:\macts\source\spikes\
=== File: C:\macts\source\spikes\ ===
Module C:\macts\source\spikes\ is missing a module doc string. Detected at line 1

Basic Metrics for module C:\macts\source\spikes\
          4    maxBlockDepth
         12    numBlocks
       3726    numCharacters
          2    numClasses
         15    numComments
          5    numFunctions
         24    numKeywords
        104    numLines
        668    numTokens

         14.42 %Comments

Functions DocString present(+) or missing(-)
- DarkMatterLogger.__init__
- DarkMatterLogger.sendMessage
- DarkMatterViewer.__init__
- DarkMatterViewer.__init__.msg_consumer
- main

Classes DocString present(+) or missing(-)

- DarkMatterLogger
- DarkMatterViewer

McCabe Complexity Metric for file C:\macts\source\spikes\
          1    DarkMatterLogger.__init__
          1    DarkMatterLogger.sendMessage
          1    DarkMatterViewer.__init__
          2    DarkMatterViewer.__init__.msg_consumer
          1    __main__
          4    main

COCOMO 2's SLOC Metric for C:\macts\source\spikes\
         55    C:\macts\source\spikes\
*** Processed 1 module in run ***

Process finished with exit code 0 is a tool for doing code coverage analysis.  Download it here:  If you have a 64bit installation you’ll want to make sure you use the .tar.gz and not succumb to using a prepackaged exe.

Downloaded the coverage-3.5.1.tar.gz version.  Extract folder from gzipped tar file.  Chang to directory of download and: python install  Now if look in c:\python27\lib\site-packages will see coverage-3.5.1-py2.7.egg Look in the scripts dir and a coverage.exe and will be seen.

Gather metrics on your code with: coverage run

Then get the report with: coverage report -m

The -m says show the line #s of statements that were not executed.  Use coverage erase to get rid of previously run data.  During my experimenting every run would get rid of previous data. 

Set up as an external tool in PyCharm like other tools.  Except had to do one for the run and another for the report.  Others are integrating into their environment using nose.

Name: Coverage

For program: C:\Python27\Scripts\coverage.exe

For parameters: run $FileName$

Working directory: $FileDir$

Name: Coverage Report

For program: C:\Python27\Scripts\coverage.exe

For parameters: report -m

Working directory: $FileDir$

Coverage Sample Output

C:\Python27\Scripts\coverage.exe run C:\macts\source\spikes\
Ran 11 tests in 0.004s


Process finished with exit code 0

Coverage Report Sample Output

C:\Python27\Scripts\coverage.exe report -m
Name             Stmts   Miss  Cover   Missing
arguments           33      0   100%  
argumentstests      45      0   100%  
TOTAL               78      0   100%  

Process finished with exit code 0


By integrating these three tools into your development process you’ll increase the community acceptance of the code you produce as well as increase the quality of the code you produce.

Getting the Enron mail database into MongoDB


In order to get some experience working with Python and MongoDB I decided I would like to find a data source with a lot of free form text. This would give me experience in pulling the data into MongoDB and at a future date I’ll have a ready data source for use with learning NLTK.
Finding a large dataset that met my needs turned out to be harder than expected. I came across Hilary Mason’s link page of research-quality data sets and found the Enron email dataset. This data set contains over 500K emails. The emails are in individual files stored in a directory structure. To me, the first step in being able to use the data is to get it into a database where I could query it.

The environment

The code was developed on an Intel Core-I7 machine with 6G of RAM and a 5400RPM hard disk. This code is I/O intensive and could have benefitted from a faster hard disk or an SSD. The host OS was Ubuntu 11.04 64bit. The tools used were Python 2.7 with pymongo and MongoDB.

The code

How to query

You can use the mongo shell to do some queries once you have loaded the data.
“use the enron_mail” database and you can do the following:
db.messages.find({ contents : /query text/i }).limit(1).skip(0);
Besides content, the document structure also includes: mailbox, subFolder and filename.
Here are some additional links with material on the shell and how to query:


Important things to note about the code:

  • change the MAIL_DIR_PATH variable to match your installation.
  • getFileContents decodes the text as being in cp1252 character set
  • saveToDatabase encodes the text in utf-8 for mongo compatibility
  • The os.walk method is key to the simplicity of this code

  • Here are some references on unicode:
    The full run took ~21 minutes after an initial run that probably had a bunch of files in cache. The run maxed out a single core of the CPU. The process was i/o bound with the hard drive. The full 6G of RAM was in use on the machine
    My query of MonogoDB says I have 517,424 emails in the document store. It shouldn’t be too difficult to modify the code to work with your database of choice.
    I hope you find this code useful and that it enables you to do some analysis with this dataset.


    Brendan McAdams @rit created a version of the code which utilizes the Python email library to produce a database with more metadata.  You can see the results of his work here: