Lib/linecache.py

   1 """Cache lines from files.
   2
   3 This is intended to read lines from modules imported -- hence if a filename
   4 is not found, it will look down the module search path for a file by
   5 that name.
   6 """
   7
   8 import sys
   9 import os
  10
  11 __all__ = ["getline","clearcache","checkcache"]
  12
  13 def getline(filename, lineno):
  14     lines = getlines(filename)
  15     if 1 <= lineno <= len(lines):
  16         return lines[lineno-1]
  17     else:
  18         return ''
  19
  20
  21 # The cache
  22
  23 cache = {} # The cache
  24
  25
  26 def clearcache():
  27     """Clear the cache entirely."""
  28
  29     global cache
  30     cache = {}
  31
  32
  33 def getlines(filename):
  34     """Get the lines for a file from the cache.
  35     Update the cache if it doesn't contain an entry for this file already."""
  36
  37     if filename in cache:
  38         return cache[filename][2]
  39     else:
  40         return updatecache(filename)
  41
  42
  43 def checkcache():
  44     """Discard cache entries that are out of date.
  45     (This is not checked upon each call!)"""
  46
  47     for filename in cache.keys():
  48         size, mtime, lines, fullname = cache[filename]
  49         try:
  50             stat = os.stat(fullname)
  51         except os.error:
  52             del cache[filename]
  53             continue
  54         if size != stat.st_size or mtime != stat.st_mtime:
  55             del cache[filename]
  56
  57
  58 def updatecache(filename):
  59     """Update a cache entry and return its list of lines.
  60     If something's wrong, print a message, discard the cache entry,
  61     and return an empty list."""
  62
  63     if filename in cache:
  64         del cache[filename]
  65     if not filename or filename[0] + filename[-1] == '<>':
  66         return []
  67     fullname = filename
  68     try:
  69         stat = os.stat(fullname)
  70     except os.error, msg:
  71         # Try looking through the module search path.
  72         basename = os.path.split(filename)[1]
  73         for dirname in sys.path:
  74             # When using imputil, sys.path may contain things other than
  75             # strings; ignore them when it happens.
  76             try:
  77                 fullname = os.path.join(dirname, basename)
  78             except (TypeError, AttributeError):
  79                 # Not sufficiently string-like to do anything useful with.
  80                 pass
  81             else:
  82                 try:
  83                     stat = os.stat(fullname)
  84                     break
  85                 except os.error:
  86                     pass
  87         else:
  88             # No luck
  89 ##          print '*** Cannot stat', filename, ':', msg
  90             return []
  91     try:
  92         fp = open(fullname, 'rU')
  93         lines = fp.readlines()
  94         fp.close()
  95     except IOError, msg:
  96 ##      print '*** Cannot open', fullname, ':', msg
  97         return []
  98     size, mtime = stat.st_size, stat.st_mtime
  99     cache[filename] = size, mtime, lines, fullname
 100     return lines