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(filename=None):
  44     """Discard cache entries that are out of date.
  45     (This is not checked upon each call!)"""
  46
  47     if filename is None:
  48         filenames = cache.keys()
  49     else:
  50         if filename in cache:
  51             filenames = [filename]
  52         else:
  53             return
  54
  55     for filename in filenames:
  56         size, mtime, lines, fullname = cache[filename]
  57         try:
  58             stat = os.stat(fullname)
  59         except os.error:
  60             del cache[filename]
  61             continue
  62         if size != stat.st_size or mtime != stat.st_mtime:
  63             del cache[filename]
  64
  65
  66 def updatecache(filename):
  67     """Update a cache entry and return its list of lines.
  68     If something's wrong, print a message, discard the cache entry,
  69     and return an empty list."""
  70
  71     if filename in cache:
  72         del cache[filename]
  73     if not filename or filename[0] + filename[-1] == '<>':
  74         return []
  75     fullname = filename
  76     try:
  77         stat = os.stat(fullname)
  78     except os.error, msg:
  79         # Try looking through the module search path.
  80         basename = os.path.split(filename)[1]
  81         for dirname in sys.path:
  82             # When using imputil, sys.path may contain things other than
  83             # strings; ignore them when it happens.
  84             try:
  85                 fullname = os.path.join(dirname, basename)
  86             except (TypeError, AttributeError):
  87                 # Not sufficiently string-like to do anything useful with.
  88                 pass
  89             else:
  90                 try:
  91                     stat = os.stat(fullname)
  92                     break
  93                 except os.error:
  94                     pass
  95         else:
  96             # No luck
  97 ##          print '*** Cannot stat', filename, ':', msg
  98             return []
  99     try:
 100         fp = open(fullname, 'rU')
 101         lines = fp.readlines()
 102         fp.close()
 103     except IOError, msg:
 104 ##      print '*** Cannot open', fullname, ':', msg
 105         return []
 106     size, mtime = stat.st_size, stat.st_mtime
 107     cache[filename] = size, mtime, lines, fullname
 108     return lines