Discovering Python by David Beazley

Transcript

1. Discovering Python David Beazley (@dabeaz) http:/ /www.dabeaz.com PyCon'2014 Montreal
2. In 2005... ... I was hired to go look at 1.5 TB (yes, that's Terabytes) of source code sitting in a secret vault.
3. Six Years Later... I testified in US district court about: - Concurrency - Threads - Event loops - Interrupts Good god!
4. Discovering with Python (or what happens when Python is brought into the ring of a legal battle)
5. Disclaimer Everything in this talk actually happened Names and details have been changed Non-disclosure (I'd have to kill you) All exhibits/photos are fictional I know nothing, you'll learn nothing
6. Meet Alice
7. Alice Meet Bob
8. Alice Bob "No, I'll send YOU a message!"
9. Alice Bob Bob's Attorney
10. Alice Bob Bob's Attorney "Bwhahahaha!" Patent Infringement
11. Alice Bob Bob's Attorney "Prepare to die!" Alice's Attorney
12. Let's Talk Patents A hot-button issue Myth: All patent lawsuits are trolls Myth: All patent lawsuits involving software are purely about software Fact: Patent litigation is hell
13. Patent Litigation You hear about patents a lot But what actually happens? This talk is about that! Initial Complaint Fact Discovery (9-12 months) Claim Construction Summary Judgement Trial
14. Plaintiff Bob "Obvious Infringement"
15. Defendant Alice "Obviously Different"
16. Fact Discovery Bob's Attorney Alice's Attorney Facts
17. "Just the facts, ma'am" Enter: Fact Expert Technical expert Unbiased party Privileged Works with legal
18. The Team Bob's Attorney Bob's Coworkers Fact Expert
19. Reality Bob's Attorney Bob's Coworkers Fact Expert
20. Reality Bob's Attorney Bob's Coworkers Fact Expert Me
21. What Happens You are dropped into a firestorm No technical guidance Because no one knows anything... that's why they called you!
22. Quick Learning The Invention
23. Quick Learning The Invention 7. The system of claim 5 or 6, wherein the display and input means comprises displays means and input means, the input means being connected to the central processing unit, the display means being connected to the slithering means and the central processing unit, the display means being arranged to display the displays and the input means transferring the input responses to the central processing unit, and wherein the display and input task means further comprises display task means and input task means, the display task means being arranged to control the display means by transferring display commands to, and receiving the display responses from, the display means, the input task means being arranged to control the input means by transferring input commands to, and receiving input responses from, the input means. The Patent
24. Quick Learning The Invention 7. The system of claim 5 or 6, wherein the display and input means comprises displays means and input means, the input means being connected to the central processing unit, the display means being connected to the slithering means and the central processing unit, the display means being arranged to display the displays and the input means transferring the input responses to the central processing unit, and wherein the display and input task means further comprises display task means and input task means, the display task means being arranged to control the display means by transferring display commands to, and receiving the display responses from, the display means, the input task means being arranged to control the input means by transferring input commands to, and receiving input responses from, the input means. The Patent
25. Invention has some code - 600 pages C - PDF - 1989
26. Patent Compilation Does the patent even work? Would the code compile? Can it be explained to others? You'd better find out How?
27. Hand Compilation from PDF - Use highlighter
28. Enter Python definitions = { 450: [ 'spam', 'grok', ], 451: [ 'foo', ], 452: [ 'bar', ] } definitions calls = { 123: [ 'blah', 'read_input', 'send_msg', ], 124: [ 'spam', 'foo', 'bar' ] } calls Entered by hand (from paper copy) A long weekend
29. Just Link It symbols = { name: pageno for pageno, defns in definitions.items() for name in defns } unresolved = [ (name, pageno) for pageno, clist in calls.items() for name in clist if name not in symbols ] missing = defaultdict(list) for name, pageno in unresolved: missing[name].append(pageno) for item in missing.items() print("Missing: %s on pages %s" % item)
30. Secret Weapons List/dict/set comprehensions collections module
31. WHY?!?!?!?! Due diligence You'd better understand your side's invention Otherwise, you will die
32. Meet The Enemy Alice
33. Meet The Enemy Alice Alice's Ninja Rockstar Coders
34. Alice's Ninja Rockstar Coders Meet The Enemy Alice
35. Meet The Enemy Alice Alice's Adult Engineers SEI CMMI Level 4
36. 5,000 pages Can you look at it? They gave us some printouts
37. Some Documents 500 pages
38. 500 pages 5,000 pages Some Documents
39. 500 pages 5,000 pages 500,000 pages Some Documents
40. (what's better than one? 300,000 that's what!) Sample Documents
41. Purported Source Code? ATTORNEY EYES ONLY ATTORNEY EYES ONLY 1677723 1677724
42. From: Guido van Rossum <guido@python.org> Date: Dec 9 23:21:42 CET 2011 Subject: [Python-Dev][PATCH] Adding braces to __future__ For me, if I had to design a new language today, I would probably use braces, not because they're better than whitespace, but because pretty much every other lanugage uses them, and there are more interesting concepts to distinguish a new language. That said, I don't regret that Python uses indentation, and the rest I have to say about the topic would violate the above request. -- --Guido van Rossum (python.org/~guido) Emails
43. From: Guido van Rossum <guido@python.org> Date: Dec 9 23:21:42 CET 2011 Subject: [Python-Dev][PATCH] Adding braces to __future__ For me, if I had to design a new language today, I would probably use braces, not because they're better than whitespace, but because pretty much every other lanugage uses them, and there are more interesting concepts to distinguish a new language. That said, I don't regret that Python uses indentation, and the rest I have to say about the topic would violate the above request. -- --Guido van Rossum (python.org/~guido) Emails Smoking gun?!?
44. Alleged Prior Art
45. Deposition of Crazy Old Guy Prior art
46. We Have Their Software It's highly proprietary You're the only one approved to look at it It's actually sitting over in a vault AKA: Software escrow
48. The Vault
49. The Vault By the tracks
50. The Vault By the tracks Rock band rehearsal space
51. Vault Protocol No computers No phone No electronics No storage devices Pen, paper and books okay
52. The Vault PC in a locked cage (no network) Printer Special paper Log Book
53. What's There? A collection of large hard drives D:\ E:\ F:\ G:\ Each containing copies of CDs (>1.5 TB total) No documentation or organization
54. Perspective Software archive for the infringing invention
55. Perspective Software archive for the infringing invention Embedded Microcontroller System
56. Perspective Software archive for the infringing invention Embedded Microcontroller System Display Module Keypads 7-segment
57. Perspective Software archive for the infringing invention Embedded Microcontroller System Display Module Keypads 7-segment A PC
58. Perspective Software archive for the infringing invention Embedded Microcontroller System Display Module Keypads 7-segment A PC Custom PCI Board
59. Perspective Software archive for the infringing invention Embedded Microcontroller System Display Module Keypads 7-segment A PC Custom PCI Board Second PC
60. Perspective A PC Custom PCI Board Second PC Custom Router Actually, more of a distributed system
61. Perspective The software is "all stack" (a million lines of code) C++/ Win32 C/ASM DCOM/ CORBA C/ASM C/ASM VB Java RMI RTOS
62. Enter Time OS/2 90 92 94 95 96 97 98 00 01 WinNT V1 V2 V3 V4 V5 V6 V7 V8 V9 RevA RevB RevC • Weekly snapshots (52 x 15 years = 780 versions) • Multiple hardware revisions/configurations • Operating system changes/deployment changes
63. Enter Customers • Dozen major customers (corporations) • Customer-specific system modifications • Think "skins" on main system • Hundreds of interlocking versions Base System Version 2.51 ACME Vers 1.23 Buy N Large Vers 4.22 Tyrell Corp Vers 3.43
64. Provided Tools Windows-XP
65. Provided Tools Windows-XP Command Prompt
66. Provided Tools Windows-XP Command Prompt Search Mutt
67. Provided Tools Notepad
68. Official Tools Notepad Visual Studio
69. Printing You can print anything Must be logged Numbered, copied, given to opposing side
70. Constraints No working hardware setup (can't run code) No working build environ (can't compile) No tech support (can't call anyone) Fragmentary documentation (if any)
72. Secret Weapon
73. Python? What? How? Unknown: How did Python get placed on the machine in the vault? I have NO idea A new IBM PC with only "approved tools" Best Guess: Used by an IBM OEM tool (Yet, there it was, python... in the Windows path no less).
74. Desert Island Coding Admit it, you've probably thought Python might be a good choice Batteries included FOR THE WIN!
75. Strategy Create a fact discovery environment from scratch in the vault I was destined for this job... I wrote the book
76. Question: What are the objectives? (What does it mean to "look at" the code?)
77. Goals What was provided? Is it complete? How does the code work? Where is the patent in the code?
78. The Horror! The Horror! Reverse engineering the entire build environ Makefiles, config files, etc. Identifying all major software components Examples: .exe files, .DLLs, plugins, etc. Sorting out version histories
79. MKDEP= mkdep SHELL= /bin/sh # === Fixed definitions === OBJS= \ bltinmodule.o \ ceval.o cgensupport.o compile.o \ errors.o \ frozen.o \ getargs.o getcompiler.o getcopyright.o getmt getplatform.o getversion.o graminit.o \ import.o importdl.o \ marshal.o modsupport.o mystrtoul.o \ pythonrun.o \ sigcheck.o structmember.o sysmodule.o \ traceback.o \ $(LIBOBJS) LIB= libPython.a Sources Library You try to figure it out
81. Basic Tooling Reimplement Unix find grep wc diff tail head Because that Windows search mutt must die
82. Example: navigation import os def cd(dirname): os.chdir(dirname) def pwd(): print(os.getcwd()) def ls(dirname=''): os.system('dir %s' % dirname)
83. Example: diff # diff.py import sys, difflib def diff(fromfile, tofile): fromlines = open(fromfile).readlines() tolines = open(tofile).readlines() diff = difflib.context_diff(fromlines, tolines, fromfile, tofile) sys.stdout.writelines(diff)
84. Interactive Shell >>> cd('pycode') >>> pwd() D:\Files\pycode >>> diff('Python-2.6/Lib/collections.py', ... 'Python-2.6.2/Lib/collections.py') *** Python-2.6/Lib/collections.py --- Python-2.6.2/Lib/collections.py *************** *** 103,109 **** # where the named tuple is created. Bypass this step in e where # sys._getframe is not defined (Jython for example). if hasattr(_sys, '_getframe'): ! result.__module__ = _sys._getframe(1).f_globals['__nam return result --- 103,109 ---- # where the named tuple is created. Bypass this step in e where # sys._getframe is not defined (Jython for example).
85. More Than Reinvention Actually implementing an entire workflow Building up layers of tools/analyses Not unlike what is done with IPython NB Can't understate Python awesomeness
86. Example def allfiles(topdir): return ((path, filename) for path, dirs, files in os.walk(topdir) for filename in files) >>> files = allfiles('AllPython') >>> next(files) ('AllPython/0/python-0.9.1', 'python.man') >>> next(files) ('AllPython/0/python-0.9.1', 'README') >>>
87. Example def filetypes(topdir): from collections import Counter from pprint import pprint c = Counter(os.path.splitext(name)[1] for _, name in allfiles(topdir)) pprint(c.most_common()) >>> filetypes('AllPython') [('.py', 125277), ('.c', 27200), ('', 17010), ('.rst', 15439), ('.h', 14782), ('.tex', 12257), ... allfiles()
88. Example def find(topdir, pattern): from fnmatch import fnmatch return ((path, name) for path, name in allfiles(topdir) if fnmatch(name, pattern)) >>> f = find('AllPython', '*.py') >>> next(f) ('AllPython/0/python-0.9.1/demo/scripts', 'findlinksto.py') >>> next(f) ('AllPython/0/python-0.9.1/demo/scripts', 'mkreal.py') >>> next(f) ('AllPython/0/python-0.9.1/demo/scripts', 'ptags.py') >>> allfiles() filetypes()
89. Example def create_versions(topdir): import re for path, _ in find(topdir, 'pgen.c'): pypath, _ = os.path.split(path) version = re.search(r'-(\w+\.\w+(\.\w+)?)$', pypath).group(1) yield version, pypath allfiles() filetypes() find()
90. Example >>> vers = find_versions('AllPython') >>> next(vers) ('0.9.1', 'AllPython/0/python-0.9.1') >>> next(vers) ('1.0.1', 'AllPython/1/python-1.0.1') >>> allfiles() filetypes() find() find_versions()
91. Example def write_manifest(topdir): import csv f =!open('manifest.csv','w') csv.writer(f).writerows(find_versions(topdir)) f.close() allfiles() filetypes() find() find_versions()
92. Example allfiles() filetypes() find() find_versions() write_manifest()
93. Example allfiles() filetypes() find() find_versions() write_manifest() .csv Workflows!
94. Pile it Higher and Higher HDDs Snapshots "Virtual File System" View View View You keep building abstractions Reorganized file layer Different views (version, date, prod, debug, etc.) .csv
95. Timeline/Inventory Tools Link together every version of every component found Development timelines Official vs. Debug releases V1 V2 V3 V4 release release release release release release release
96. Example: Versioning def versions(filename): import hashlib from collections import defaultdict manifest = read_manifest() groups = defaultdict(list) for vers, path in manifest.items(): fullname = os.path.join(path, filename) if os.path.exists(fullname): digest = hashlib.new('md5') digest.update(open(fullname,'rb').read()) groups[digest.digest()].append(vers) return sorted([sorted(g) for g in groups.values()])
97. Example: Versioning >>> for x in versions('Python/thread.c'): ... print(x) ... ['1.0.1'] ['1.1'] ['1.2', '1.3'] ['1.4'] ['1.5', '1.5.1'] ['1.5.2', '1.5.2c1'] ['1.5.2b1', '1.5.2b2'] ['1.6', '1.6b1'] ['2.0', '2.0.1', '2.0c1', '2.1', '2.1.1', '2.1.2', '2.1.3'] ...
98. Navigational Tooling "Virtual File System" View View View Query tools for going to any version/file Navigational Tools >>> view('2.7.3', 'Python/ceval.c') >>> Typically launch windows tools (e.g., Vis Studio)
99. Commentary I don't know if the opposing side actually expected us to figure out their code We knew almost everything about everything Python FOR.THE.WIN.
100. How Does Code Work? Better make sure you understand everything about the code Software architecture Interaction between components Underlying algorithms
101. Problem: Code Sucks Nobody wants to read code Better: Design documents, specs Nobody wants to give you that "Go read the source."
102. Let's Go Fishing Interesting files Code comments TPS reports PDF, DOC, RTF, HTML, TXT / / See: Important Document Fixed bug. See important specification. I ὑ re
103. Back and Forth An obscure find /* See FS-6541-8v2.0 for details */ A request to attorneys "Tell opposing counsel we can't find FS-6541-8v2.0" A few silent days pass....
107. Casting a Wide Net Search for documents is far and wide Software change notices Unrelated software (peripheral devices) Emails The web (catalogs, manuals, job postings, etc.) Analogy: Pulling on a loose thread...
108. Commentary You're learning the invention from scratch Reading other people's code You're teaching attorneys about it The other side doesn't want you to succeed You will learn A LOT in this exercise
109. Some Lessons Learned SUCKS ROCKS C++ Assembly code Asynchronous Threads Objects Functions Makefiles IDEs CASE Tools Humans 1990s 1970s (of course this is just my opinion, I could be wrong) UML Words
110. Speaking of Attorneys Do the "facts" support patent infringement? Does it look like it infringes? Can it be proven that it infringes? (Let the game begin)
112. Remember this? 7. The system of claim 5 or 6, wherein the display and input means comprises displays means and input means, the input means being connected to the central processing unit, the display means being connected to the slithering means and the central processing unit, the display means being arranged to display the displays and the input means transferring the input responses to the central processing unit, and wherein the display and input task means further comprises display task means and input task means, the display task means being arranged to control the display means by transferring display commands to, and receiving the display responses from, the display means, the input task means being arranged to control the input means by transferring input commands to, and receiving input responses from, the input means. The Patent
113. Remember this? 7. The system of claim 5 or 6, wherein the display and input means comprises displays means and input means, the input means being connected to the central processing unit, the display means being connected to the slithering means and the central processing unit, the display means being arranged to display the displays and the input means transferring the input responses to the central processing unit, and wherein the display and input task means further comprises display task means and input task means, the display task means being arranged to control the display means by transferring display commands to, and receiving the display responses from, the display means, the input task means being arranged to control the input means by transferring input commands to, and receiving input responses from, the input means. The Patent What does this claim mean? (let's rumble)
115. Defining Claim Terms 7. The system of claim 5 or 6, wherein the display and input means comprises displays means and input means, the input means being connected to the central processing unit, the display means being connected to the slithering means and the central processing unit, the display means being arranged to display the displays and the input means transferring the input responses to the central processing unit, and wherein the display and input task means further comprises display task means and input task means, the display task means being arranged to control the display means by transferring display commands to, and receiving the display responses from, the display means, the input task means being arranged to control the input means by transferring input commands to, and receiving input responses from, the input means. The Patent Term Plaintiff Defendant central processing unit display means
116. Claim Construction Claim terms have to be supported by reality If not, it's game over A lot of attorney/expert consultation Problem: very specific facts and structure File: Widget/foo.c, lines 230-255. Requires a deep dive
117. Problem Matching claims to 800 versions of a million line program Pick one version? Which one? Match them all?
118. Fragment Versioning You're familiar with source code control Imagine applying it to code fragments/excerpts In reverse Hmmm.
119. /* source.c */ void grok() { if (spam) { foo(); bar(); } ... } void blah() { ... }
120. /* source.c */ void grok() { if (spam) { foo(); bar(); } ... } void blah() { ... } file: source.c start: 'void grok()' end: 'void blah()' Fragment
121. /* source.c */ void grok() { if (spam) { foo(); bar(); } ... } void blah() { ... } file: source.c start: 'void grok()' end: 'void blah()' Fragment Snapshots (>800) Global fragment search across all versions
122. /* source.c */ void grok() { if (spam) { foo(); bar(); } ... } void blah() { ... } file: source.c start: 'void grok()' end: 'void blah()' Fragment Snapshots (>800) Ver1 Ver2 Ver3 void grok() { if (spam) { foo(); bar(); } } void blah() { void grok() { if (spam) { foo(); bar(x); } } void blah() { void grok() { if (spam) { new_foo(); bar(x); } } void blah() {
123. Big Picture Reduce a massive data set to something sane "This claim matches this structure in the code. There have only been six versions of this code over 15 years. Here are the six versions."
124. PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON
125. PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON Python makes the impossible possible
126. PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON PYTHON Python makes the impossible possible (even Python 3)
127. Final Thoughts If you get the chance to do this, do it! You will learn A LOT! Would I want to do it again? Not sure.
128. But How Did it End?
130. My End Game I learned a lot about generator functions Ultimately a well-known PyCon tutorial...
131. Postscript: Expert Report You may be asked to write an expert report Outlines all factual findings Ties facts to patent claims A scientific document It's a document that WILL be read
132. Postscript: Deposition You A room of attorneys Opposing expert Court reporter Videographer 8 hours It will be one of the most intense, surreal, awesome/worst experiences of your whole life.
133. Postscript: Court Testimony Like deposition, but dialed up to 11 Twice as many attorneys, more experts Judge & clerks
134. Questions