Lifehack - import directly from command line

If you're obsessed with UX as I am, and long repetitive commands seem to break your flow, you may appreciate this little trick for invoking Python from command line.

I invoke python from console/terminal to check some behavior that I tend to forget after a day in JavaScript or other programming languages. It is often way faster than reading the docs. It also helps to quickly try new PyPI libraries after installing with pip (saves on mouse clicking in IDE etc.).

Today I found a time saver that makes me happy. This example is typed for Windows, but there should be no problem for any Linux hacker to port it to their favorites. So instead of doing this:

> python [ENTER]
>>> import os [ENTER]
>>> os.name [ENTER]
'nt'

I can just type:

> import os [ENTER]
>>> os.name [ENTER]
'nt'

It should be now easy to understand how it works, so I will complicate it a bit. The trick is this little import.bat script, placed in system PATH:

@echo off
py -2 -c "import sys; print(sys.version)"
py -2 -i -c "import %*"

py here is a py.exe launcher that can call either Python 2 or Python 3 depending on argument. It comes installed with Windows Python versions. I like to know which Python I work with, so I've added version into to the command, and to avoid polluting the global space of new interpreter, the version is printed by separate command.

ANN: hexdump 2.0 - view/edit your binary with hex tool

https://pypi.python.org/pypi/hexdump

Finally some prod that can be named feature-complete for release. It is cross-platform, meaning it should run the same on Windows (tested), Linux, and OS X. It is Python 2 and Python 3 compatible. And it released into public domain, so that you won't have any problems in reusing it for your commercial and non-commercial hacking.

For those who are unaware of what hexdump is, hexdump is a representation of any binary data in human readable form. This form is good for hacking, inspecting and debugging binary data and protocols, but it is also good for editing such data. I am not pasting the output if the tool to encourage you to play with it yourself.

It can be used as command line tool and as a library. The most simple way is to use it as a tool:

# install
$ python -m pip install hexdump

# dump
$ python -m hexdump binary.bin > dump.txt
...

# restore
$ python -m hexdump --restore dump.txt
...

P.S. I don't mind including `hexdump` as provisional package in Python standard library if anyone will be able to convince PSF to accept public domain, CC0 or MIT licensed code.

hgsubversion: Installing on Windows

I use Windows primarily, and it's not easy to install Mercurial extensions there if they are not bundled with Mercurial installer itself. I am using plain .msi installer, which doesn't include hgsubversion, so I'll show you how to get this extension in place manually. Suppose you have Mercurial installed into C:\Mercurial Go there and notice library.zip archive. This is where you should add hgsubversion. library.zip has the following structure: / +-- email +-- encodings +-- hgext +-- logging ... __future__.pyc _abcoll.pyc _elementtree.pyd ... zipextimporter.pyc zipfile.pyc Contents of this archive is the whole Mercurial code. Code is written in Python, and is compiled into .pyc and .pyd files for speed and packed into library.zip for convenience. For interpreted languages like Python it is not necessary to compile source files for execution, but they did it. Get latest hgsubversion sources from http://bitbucket.org/durin42/hgsubversion/src by pressing link "get source" in upper right corner. Or download released version from http://pypi.python.org/pypi/hgsubversion/1.1.2 Unpack archive. You should have directory structure like: / +-- hgsubversion +-- notes +-- tests +-- tools .hgignore ... setup.py Now put hgsubversion/ dir from this structure into library.zip archive, inside hgext/ directory, where Mercurial expects to find its extensions. Enable extension by uncommenting line ";hgsubversion =" in Mercurial.ini that is usually located in your profile directory, i.e. C:\Users\yourname If it is not there - copy one from your C:\Mercurial\hgrc.d directory. Try to checkout some subversion repository. You will get an error like this: C:\p>hg clone http://google-twitter.googlecode.com/svn/trunk (falling back to static-http) (falling back to Subversion support) destination directory: trunk abort: subvertpy 0.7.3 or later required, but not found! You need Subversion bindings for Python. They advertise subvertpy, but it is also possible to use official bindings. Those bindings is just a set of libraries that allows Python scripts to use Subversion binary code directly. Unfortunately, after migration to apache.org, Subversion bindings are not compiled anymore, so there is no official place where you can download them. But thanks to http://alagazam.net/ it is possible to get unofficial . Download svn-win32-1.6.12_py.zip or more up-to-date distribution and extract it. You will get a directory structure like: / +-- python +-- libsvn +-- svn README.txt In libsvn/ rename _client.dll to _client.pyd. Do the same with _core.dll, _delta.dll, _ra.dll Maybe you'll have to rename other .dll files, but these were enough for me. Now put svn/ and libsvn/ into the library.zip directly in the root. I also had to copy intl3_svn.dll from an old 1.6.6 installation of SVN into library.zip root (you may find this file in Windows binaries archive from http://alagazam.net/) and place libsvn_swig_py-1.dll from libsvn/ dir also in library.zip root. It should work now. 

URL parameters in action method of HTML form are lost for GET request

Surprisingly how experienced web-developers may miss some basic nuances of form processing that exist for many-many years. One of them is the fact that URL parameters added to action attribute of <form> element are lost for GET requests.

Example:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Query string from action attribute is killed for GET request</title>
</head>
<body>

  <form name="getSearchForm" action="?missed=one" method="get">
    <input type="text" name="q" value="s" />
    <button class="searchButton" type="submit">GET</button>
  </form>

  <form name="postSearchForm" action="?missed=one" method="post">
    <input type="text" name="q" value="s" />
    <button class="searchButton" type="submit">POST</button>
  </form>

</body>
</html> 
The parameter "missed=one" is missing from URL after clicking a button on a form with GET send method. It is present for POST form though.