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  1. <html>
  2. <STYLE type="text/css">
  3.    H1 {border-width: 1; border: solid}
  4.  </STYLE>
  5. <title>Scripting Column as of $Date: 2004/08/20 $</title>
  6. <h1><center>Monthly Scripting Column for April</center></h1>
  7. <table border=0 width="100%">
  8. <tr><td width="70%">
  9. <p>Greetings!
  10. This continues a series of bulletins, in which we introduce
  11. one of the scripts that will be in a future release.
  12. <td>
  13.     <table border=1 width="100%">
  14.     <tr><td><i><font color="blue">Tip: don't like the output? Use 'p4 -G' output as input to your Python script, and format the data (or graph it) to your liking.</font></i>
  15.     </table>
  16. </tr>
  17. </table>
  18. <hr>
  19. <h2>Today's script</h2>
  20. <p><b>Leverage off other work.</b>
  21. We hear this often, and say it in this column a lot, too.
  22. The most error-prone programming I encounter is data validation code.
  23. That's the stuff that
  24. reads input, validates it, etc. Any chance I get to use code
  25. that someone else has already created (and tested), I'll take.
  26. <p>
  27. To that end, there's a facility available to Python programmers
  28. for retrieving that data from a Perforce query without parsing
  29. through formatted output.
  30. This option, &quot;p4 -G&quot;, retrieves Perforce data to be read
  31. by a Python program:
  32. <pre>      p4 <font color="red">-G</font> clients  | python program.py </pre>
  33. Today's example retrieves that output using the
  34. Python library routine, <em>os.popen</em>.
  35. <p>
  36. The &quot;-G&quot; option, which went between <em>p4</em> and <em>clients</em>,
  37. sets the output option to a binary format.
  38. That format is called &quot;marshal&quot;, and is a representation
  39. of a Python variable or object.
  40. <p>
  41. You can read such output with this routine written in Python,
  42. which runs a Perforce command and
  43. returns the results of the 'p4' command. The results are
  44. easy for the Python programmer to use: an array of 'dict'
  45. objects.
  46. <pre>
  47. import os
  48. import marshal
  49. def runp4cmd(p4cmd):
  50.     """ Return the output from the Perforce command,
  51.     and assume that the user put the '-G' in the options
  52.     to get us marshall output.  We always return an array
  53.     for the results."""
  54.  
  55.     fd = os.popen(p4cmd, 'r')
  56.     results = []
  57.     while 1:
  58.         try:
  59.             d = marshal.load(fd)
  60.             results.append(d)
  61.         except EOFError:
  62.             break
  63.     fd.close()
  64.     return results         <em># end of runp4cmd</em>
  65.  
  66. clientList = runp4cmd('p4 -G clients')
  67. for c in clientList:
  68.     print c['client']
  69. </pre>
  70. <p>
  71. In the following example, there's a reference to the Options field.
  72. (We normally think of it as a list of strings, since that's how the
  73. client spec is formatted when we run 'p4 client.')
  74. The first thing is to burst it into an array,
  75. <em>optionList</em>,
  76. so that we can search it easily.
  77. <hr>
  78. <pre>
  79. import marshal,os, pprint,sys
  80. from readp4marshal import runp4cmd
  81.  
  82. # Task: determine which client specs have the option 'nocompress'set.
  83. #
  84. # status: tested on Win/2000 using python 2.0
  85. # num of calls to 'p4': 1
  86.  
  87. clientList = runp4cmd("p4 -G clients")
  88.  
  89. for c in clientList:
  90.     optionList = c['Options'].split(' ')
  91.     for o in optionList:
  92.         if o == 'compress':
  93.             print "%s: compression of data (default)" % c['client']
  94.         if o == 'nocompress':
  95.             print "%s: *no* compression of data" % c['client']
  96. </pre>
  97. <hr>
  98. <center><b>findnocompress.py</b></center>
  99. <hr>
  100. <small><p>Note: all the programs shown in these columns have been written four times: in Perl, in P4Perl, in Python, and in P4Ruby.  Look into the Perforce example database for the other versions.</small>
  101. <br>
  102. <i><small>$Id: //guest/jeff_bowles/scripts/0430python.html#1 $</small>
  103. <br>&copy; 2004 Perforce Corporation, Inc.</small></i>
  104. </html>
# Change User Description Committed
#1 4420 Jeff Bowles adding the beginnings of example "columns" for
    scripting examples. 		21 years ago