PyCon 2011: IronPython Command Line

WRITING COMMAND-LINE
TOOLS WITH IRONPYTHON
AND VISUAL STUDIO
Noah Gift Including PowerShell, and F#

Talk Objectives

¤  Freak you out a bit.
¤  Teach you something you
didn’t know. (Not covered in
any book).
¤  Be controversial.

¤  Entertain you.

Monty Hall Problem
¤  You are invited to a game
show.
¤  Game show host shows you
three doors.
¤  Behind two doors there is a
goat, and behind one door is
a $50,000 dollar sports car.

Monty Hall Problem
¤  You choose a door.
¤  Instead of opening your
door. The game show
host then opens up
another door, to reveal a
goat.
¤  Do you switch your
choice?

Monty Hall Problem

¤  You always switch doors:
2/3 probability versus ½
probability.
¤  Bayes Rule shows us this:
(Think Spam classification).

Monty Hall Takeaway
¤  This isn’t intuitive to most
people
¤  The human brain’s intuition
is often broken.
¤  What else is your brain
wrong about?

Windows Is The Great Satan?
¤  Command-line is feeble
¤  People on twitter say it sucks
¤  Nothing COOL ever happens
on Windows
¤  This isn’t “their” conference.

¤  What if your brain’s intuition is
wrong about this too?

I Used To Hate Windows
¨  I Grew Up
¨  New Philosophy: Write
Code in any language,
in any environment.
¨  If it is innovative, I don’t
care who made it.
¨  Sorry Stallman, we
disagree.

What do most developers and admins
think of when they hear Linux?
¨  Power ¨  The Shell
¨  Flexibility ¨  Command-tools

¨  Bash ¨  Man Pages

¨  SSH ¨  Awk/Sed

What Is The Unifying Theme Around This?
¨  String Output is King ¨  Tim O’Reilly in Unix
¨  Small Tools Power Tools, “A new
¨  Flexibility
user by stringing
together simple
¨  Geek Power.
pipelines….”

The Hardest Part of Writing a *Nix
Command-line tool in Python
¨  Remote Administration: ¨  Religious war in your
Pyro vs SSH vs ??? company over using
¨  Dealing with *Nix tools optparse, getargs,
that pass you back or argparse
unstructured text.

Python/Unix Command-line Tools: The
End Game
¨  Remote Object
Invocation (Pyro, SSH,
Fabric)
¨  Security (SSH, SSL)
¨  Automation
¨  Application API
¨  Event Management
(Pyro)
¨  Transactions (Mercurial?)

How To Write A Classic IronPython CLI
¨  I needed to upgrade 100’s of thousands of lines of
C# to .NET 4.0.
¨  I wrote a quick and dirty Command-line tool in

IronPython.

Project Upgrader: Validate Version

Step 1 def
validate_vsver(slnfile):

"""Validates
whether
a
.sln
file
has
already
been
upgraded
to
VS
2010"""

try:

project_file
=
open(slnfile)

for
project_version_line
in
project_file.readlines():

if
"Visual
Studio
2010"
in
project_version_line:

log.debug("Found
VS
2010
project
line:
%s"
%
project_version_line)

log.debug("Project
file
already
upgraded....skipping:
%s"
%
slnfile)

return
False

return
True

finally:

project_file.close()

Project Upgrader: Walk A Tree
Step 2 def
walk_tree(path,
extension="sln",

version_control_type=".svn",
exclude_path=None):

"""Walks
a
tree,
if
there
is
a
match
to
an
extension,

it
returns
a
fullpath.

Skips
version_control_type
directories,
which
by

default
is
set
to
.svn

"""

for
dirpath,dirname,filename
in
os.walk(path):

#The
walk
should
skip
version
control
directories

for
dir
in
dirname:

Project Upgrader: Convert Project

Step 3 def
convert_project(filename):

"""Converts
a
project
to
VS2010
using
deven
via
.NET
Process

Class"""

p
=
Process()

p.StartInfo.UseShellExecute
=
False

p.StartInfo.RedirectStandardOutput
=
True

p.StartInfo.RedirectStandardError
=
True

p.StartInfo.FileName
=
"""C:Program
Files
(x86)Microsoft

Visual
Studio
10.0Common7IDEdevenv.exe"""

print
"Stdout:
%s|
Stderr:
%s"
%
(stdout,
stderr)

p.WaitForExit()

return
p.ExitCode

Project Upgrader: Convert Tree

Step 4 def
convert_tree(path,
exclude_path):

"""Recursively
modifies
a
tree
of
sln
files,
if
they

haven't
been
upgraded
to
VS
2010"""

for
file
in
walk_tree(path,
exclude_path=exclude_path):

if
not
validate_vsver(file):

#we
should
pass
upgrading
if
validate_vsver

returns
False

continue

exit_code
=
convert_project(file)

log.info("%s,
%s"
%
(exit_code,
file))

Project Upgrader: Run method

Step 4
def
run(self):

args,
parser
=
self.options()

if
args.path:

exclude
=
None

if
args.exclude:

exclude
=
args.exclude

log.info("Exclude
set:
%s"
%
exclude)

log.info("%s
Running
VS2010
upgrade
on
tree:
%s
|

excluding
dirs
named:
%s"
%
(time.ctime(),
args.path,
exclude))

convert_tree(args.path,
exclude_path=exclude)

else:

parser.print_help()

Python is like Kudzu
¤  Itsstrength is that it can
embed itself into any project,
any operating system.
¤  Not always the best tool, but
often good enough.

Who Is The Target Audience For
Command-line Tools?
¤  Systems Administrators
¤  Power Users
¤  Developers

¤  Systems Integrators/OEM

¤  Young Geeky Stallman

What Does It Really Mean To Write A
Command-line tool on Linux
¤  You have an executable that
runs in the context of, most
likely, Bash.
¤  You output a string, which you
can then pipeline into our Unix
tools, sed, awk, grep.
¤  If your nice you create –help

What Does It Really Mean To Write A
Command-line tool on Modern Windows
¤  Itis going to run inside of
PowerShell. PowerShell is your
bash.
¤  You have a unified interface
to .NET and every possible
high level automation API you
can think of.
¤  PowerShell tools expect
OBJECTS not strings.

PowerShell is Secure By Default
¤  Default File
Association is
Notepad or ISE.
¤  Remoting is
disabled.
¤  No execution of
scripts.
¤  Script Signing

Learning To Properly Write IronPython
Command-Line Tools: “A two minute affair”
¤  Actually no, not even close.
¤  Forget “most” of what you
know from linux.
¤  PowerShell changes
everything.

PowerShell Object Passing Changes How
Shells Work
¤  Fundamental change to
understand
¤  You need to understand this to
write command-line tools on
Windows
¤  Game changer

We’re not in a flyover state anymore
¤  String
output is lame!
¤  PowerShell wants objects
¤  What to do…what to do…

Fight the ecosystem and you will die
¤  Command-line tools should run
in PowerShell not cmd.exe.
¤  The bash/linux CPython way,
won’t cut it here.
¤  You must think the way .NET
thinks.
¤  Everything takes and returns
an Object.

PowerShell Endgame: We did
EVERYTHING for you.
¤  Encrypted, paranoid secure,
transactional, asynchronous
remoting of serialized objects
¤  High level automation API to
everything.
¤  Ignore at your own peril.

Writing a PowerShell Module In IronPython: The
“real” way to write Command-line tools?
¨  Create a New Visual Studio Project
¨  Thinks Objects

¨  Use PowerShell SDK

¨  Write a Binary Module

Installing the PowerShell SDK
¤  Download the SDK
¤  Add a reference to the DLL in your Visual Studio Project

¤ C:ProgramFiles (x86)Reference
AssembliesMicrosoftWindowsPowerShell
v1.0System.Management.Automation

Finding and Loading PowerShell Modules
¨  Get-Module –all
¨  When you create a .dll in IronPython, could then

simply integrate it into the PowerShell workflow.

What is a Binary Module?
¤  A .NET assembly compiled against PowerShell
libraries.
¨  For IronPython folks, this is one way to integrate into
PowerShell
¨  In a lot of documentation it will refer to C# code.

¨  You can also write a PowerShell, non-compiled,
module.

Creating a Binary Module For Powershell
in IronPython
¤  http://stackoverflow.com/questions/2094694/launch-
powershell-under-net-4
¤  You need to tweak some registry settings to support .NET 4.0
in PowerShell.

Creating a Binary Module For Powershell
in IronPython: Continued
¤  Should follow C# example code for best implementation
advice.
¤  Note, Argparse, Optparse, etc, aren’t used. They don’t make
sense.
¤  These are objects being passed into other cmdlets, and
methods are being called on those objects.

IronPython PowerShell Module Hello
World
Visual Studio import
clr

Project: clr.AddReference('System.Management.Automation')

print
'Hello
World'

Step 1

IronPython PowerShell Module Hello World
Visual Studio ¨  Build the project to create a .dll
Project:
¨  In PowerShell Import Module
Step 2
¨  Import-Module MyModule.dll

¨  You can know interact with it from inside

of .Net. Is this a commandline tool???

Setting Up A PowerShell Profile For IronPython
¨  Just like in Bash or
ZSH, aliases are your
friend.
¨  Edit your $profile with
the ISE, and add
interactive IronPython
to it.

Creating Standalone IronPython executables
¨  Make sure you can
pass objects in and out
of them.
¨  Use the IronPython on

codeplex: Pyc-Python
Command-line compiler

F#: The Elephant in the Room
¤  Type inference
¤  Immutable data structures
¤  Run as script or compiled

¤  Tail recursion

¤  Fully integrated with Visual
Studio
¤  Sexier then Python?

F# and Python: A Sexy Beast
¤  Mixing .dll files written in F#
into IronPython modules,
loaded into Powershell.
¤  Calling IronPython/CPython
from inside of F#
¤  “A statically typed
Python…” (Note, this will come
up..just preparing you…)

Credit Some Excellent Books That
Reference PowerShell
¤  PowerShell in Action,
Manning (The Bible)
¤  PowerShell Cookbook, O’Reilly

¤  IronPython in Action, Manning

Conclusion
¤  PowerShell isn’t a competing
language, it IS THE ECOSYSTEM.
¤  Windows Systems Admins are
using PowerShell for everything
¤  Get your head wrapped around
object based pipelines.
¤  Why doesn’t Linux have this?

Questions?
Code:
https://bitbucket.org/noahgift/pycon2011-
ironpython-cli

PyCon 2011: IronPython Command Line

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