mirror of
https://github.com/python/cpython.git
synced 2025-10-31 10:26:02 +00:00
274ad9dc81
Slightly improved the code for dealing with newline on a comment line, and for stripping whitespace.
355 lines
14 KiB
Python
355 lines
14 KiB
Python
"""text_file
|
|
|
|
provides the TextFile class, which gives an interface to text files
|
|
that (optionally) takes care of stripping comments, ignoring blank
|
|
lines, and joining lines with backslashes."""
|
|
|
|
# created 1999/01/12, Greg Ward
|
|
|
|
__revision__ = "$Id$"
|
|
|
|
from types import *
|
|
import sys, os, string, re
|
|
|
|
|
|
class TextFile:
|
|
|
|
"""Provides a file-like object that takes care of all the things you
|
|
commonly want to do when processing a text file that has some
|
|
line-by-line syntax: strip comments (as long as "#" is your comment
|
|
character), skip blank lines, join adjacent lines by escaping the
|
|
newline (ie. backslash at end of line), strip leading and/or
|
|
trailing whitespace, and collapse internal whitespace. All of these
|
|
are optional and independently controllable.
|
|
|
|
Provides a 'warn()' method so you can generate warning messages that
|
|
report physical line number, even if the logical line in question
|
|
spans multiple physical lines. Also provides 'unreadline()' for
|
|
implementing line-at-a-time lookahead.
|
|
|
|
Constructor is called as:
|
|
|
|
TextFile (filename=None, file=None, **options)
|
|
|
|
It bombs (RuntimeError) if both 'filename' and 'file' are None;
|
|
'filename' should be a string, and 'file' a file object (or
|
|
something that provides 'readline()' and 'close()' methods). It is
|
|
recommended that you supply at least 'filename', so that TextFile
|
|
can include it in warning messages. If 'file' is not supplied,
|
|
TextFile creates its own using the 'open()' builtin.
|
|
|
|
The options are all boolean, and affect the value returned by
|
|
'readline()':
|
|
strip_comments [default: true]
|
|
strip from "#" to end-of-line, as well as any whitespace
|
|
leading up to the "#" -- unless it is escaped by a backslash
|
|
lstrip_ws [default: false]
|
|
strip leading whitespace from each line before returning it
|
|
rstrip_ws [default: true]
|
|
strip trailing whitespace (including line terminator!) from
|
|
each line before returning it
|
|
skip_blanks [default: true}
|
|
skip lines that are empty *after* stripping comments and
|
|
whitespace. (If both lstrip_ws and rstrip_ws are true,
|
|
then some lines may consist of solely whitespace: these will
|
|
*not* be skipped, even if 'skip_blanks' is true.)
|
|
join_lines [default: false]
|
|
if a backslash is the last non-newline character on a line
|
|
after stripping comments and whitespace, join the following line
|
|
to it to form one "logical line"; if N consecutive lines end
|
|
with a backslash, then N+1 physical lines will be joined to
|
|
form one logical line.
|
|
collapse_ws [default: false]
|
|
after stripping comments and whitespace and joining physical
|
|
lines into logical lines, all internal whitespace (strings of
|
|
whitespace surrounded by non-whitespace characters, and not at
|
|
the beginning or end of the logical line) will be collapsed
|
|
to a single space.
|
|
|
|
Note that since 'rstrip_ws' can strip the trailing newline, the
|
|
semantics of 'readline()' must differ from those of the builtin file
|
|
object's 'readline()' method! In particular, 'readline()' returns
|
|
None for end-of-file: an empty string might just be a blank line (or
|
|
an all-whitespace line), if 'rstrip_ws' is true but 'skip_blanks' is
|
|
not."""
|
|
|
|
default_options = { 'strip_comments': 1,
|
|
'skip_blanks': 1,
|
|
'join_lines': 0,
|
|
'lstrip_ws': 0,
|
|
'rstrip_ws': 1,
|
|
'collapse_ws': 0,
|
|
}
|
|
|
|
def __init__ (self, filename=None, file=None, **options):
|
|
"""Construct a new TextFile object. At least one of 'filename'
|
|
(a string) and 'file' (a file-like object) must be supplied.
|
|
They keyword argument options are described above and affect
|
|
the values returned by 'readline()'."""
|
|
|
|
if filename is None and file is None:
|
|
raise RuntimeError, \
|
|
"you must supply either or both of 'filename' and 'file'"
|
|
|
|
# set values for all options -- either from client option hash
|
|
# or fallback to default_options
|
|
for opt in self.default_options.keys():
|
|
if options.has_key (opt):
|
|
setattr (self, opt, options[opt])
|
|
|
|
else:
|
|
setattr (self, opt, self.default_options[opt])
|
|
|
|
# sanity check client option hash
|
|
for opt in options.keys():
|
|
if not self.default_options.has_key (opt):
|
|
raise KeyError, "invalid TextFile option '%s'" % opt
|
|
|
|
if file is None:
|
|
self.open (filename)
|
|
else:
|
|
self.filename = filename
|
|
self.file = file
|
|
self.current_line = 0 # assuming that file is at BOF!
|
|
|
|
# 'linebuf' is a stack of lines that will be emptied before we
|
|
# actually read from the file; it's only populated by an
|
|
# 'unreadline()' operation
|
|
self.linebuf = []
|
|
|
|
|
|
def open (self, filename):
|
|
"""Open a new file named 'filename'. This overrides both the
|
|
'filename' and 'file' arguments to the constructor."""
|
|
|
|
self.filename = filename
|
|
self.file = open (self.filename, 'r')
|
|
self.current_line = 0
|
|
|
|
|
|
def close (self):
|
|
"""Close the current file and forget everything we know about it
|
|
(filename, current line number)."""
|
|
|
|
self.file.close ()
|
|
self.file = None
|
|
self.filename = None
|
|
self.current_line = None
|
|
|
|
|
|
def warn (self, msg, line=None):
|
|
"""Print (to stderr) a warning message tied to the current logical
|
|
line in the current file. If the current logical line in the
|
|
file spans multiple physical lines, the warning refers to the
|
|
whole range, eg. "lines 3-5". If 'line' supplied, it overrides
|
|
the current line number; it may be a list or tuple to indicate a
|
|
range of physical lines, or an integer for a single physical
|
|
line."""
|
|
|
|
if line is None:
|
|
line = self.current_line
|
|
sys.stderr.write (self.filename + ", ")
|
|
if type (line) in (ListType, TupleType):
|
|
sys.stderr.write ("lines %d-%d: " % tuple (line))
|
|
else:
|
|
sys.stderr.write ("line %d: " % line)
|
|
sys.stderr.write (str (msg) + "\n")
|
|
|
|
|
|
def readline (self):
|
|
"""Read and return a single logical line from the current file (or
|
|
from an internal buffer if lines have previously been "unread"
|
|
with 'unreadline()'). If the 'join_lines' option is true, this
|
|
may involve reading multiple physical lines concatenated into a
|
|
single string. Updates the current line number, so calling
|
|
'warn()' after 'readline()' emits a warning about the physical
|
|
line(s) just read. Returns None on end-of-file, since the empty
|
|
string can occur if 'rstrip_ws' is true but 'strip_blanks' is
|
|
not."""
|
|
|
|
# If any "unread" lines waiting in 'linebuf', return the top
|
|
# one. (We don't actually buffer read-ahead data -- lines only
|
|
# get put in 'linebuf' if the client explicitly does an
|
|
# 'unreadline()'.
|
|
if self.linebuf:
|
|
line = self.linebuf[-1]
|
|
del self.linebuf[-1]
|
|
return line
|
|
|
|
buildup_line = ''
|
|
|
|
while 1:
|
|
# read the line, make it None if EOF
|
|
line = self.file.readline()
|
|
if line == '': line = None
|
|
|
|
if self.strip_comments and line:
|
|
|
|
# Look for the first "#" in the line. If none, never
|
|
# mind. If we find one and it's the first character, or
|
|
# is not preceded by "\", then it starts a comment --
|
|
# strip the comment, strip whitespace before it, and
|
|
# carry on. Otherwise, it's just an escaped "#", so
|
|
# unescape it (and any other escaped "#"'s that might be
|
|
# lurking in there) and otherwise leave the line alone.
|
|
|
|
pos = string.find (line, "#")
|
|
if pos == -1: # no "#" -- no comments
|
|
pass
|
|
elif pos == 0 or line[pos-1] != "\\": # it's a comment
|
|
|
|
# Have to preserve the trailing newline, because it's
|
|
# the job of a later step (rstrip_ws) to remove it --
|
|
# and if rstrip_ws is false, we'd better preserve it!
|
|
# (NB. this means that if the final line is all comment
|
|
# and has no trailing newline, we will think that it's
|
|
# EOF; I think that's OK.)
|
|
eol = (line[-1] == '\n') and '\n' or ''
|
|
line = line[0:pos] + eol
|
|
|
|
else: # it's an escaped "#"
|
|
line = string.replace (line, "\\#", "#")
|
|
|
|
|
|
# did previous line end with a backslash? then accumulate
|
|
if self.join_lines and buildup_line:
|
|
# oops: end of file
|
|
if line is None:
|
|
self.warn ("continuation line immediately precedes "
|
|
"end-of-file")
|
|
return buildup_line
|
|
|
|
line = buildup_line + line
|
|
|
|
# careful: pay attention to line number when incrementing it
|
|
if type (self.current_line) is ListType:
|
|
self.current_line[1] = self.current_line[1] + 1
|
|
else:
|
|
self.current_line = [self.current_line, self.current_line+1]
|
|
# just an ordinary line, read it as usual
|
|
else:
|
|
if line is None: # eof
|
|
return None
|
|
|
|
# still have to be careful about incrementing the line number!
|
|
if type (self.current_line) is ListType:
|
|
self.current_line = self.current_line[1] + 1
|
|
else:
|
|
self.current_line = self.current_line + 1
|
|
|
|
|
|
# strip whitespace however the client wants (leading and
|
|
# trailing, or one or the other, or neither)
|
|
if self.lstrip_ws and self.rstrip_ws:
|
|
line = string.strip (line)
|
|
elif self.lstrip_ws:
|
|
line = string.lstrip (line)
|
|
elif self.rstrip_ws:
|
|
line = string.rstrip (line)
|
|
|
|
# blank line (whether we rstrip'ed or not)? skip to next line
|
|
# if appropriate
|
|
if line == '' or line == '\n' and self.skip_blanks:
|
|
continue
|
|
|
|
if self.join_lines:
|
|
if line[-1] == '\\':
|
|
buildup_line = line[:-1]
|
|
continue
|
|
|
|
if line[-2:] == '\\\n':
|
|
buildup_line = line[0:-2] + '\n'
|
|
continue
|
|
|
|
# collapse internal whitespace (*after* joining lines!)
|
|
if self.collapse_ws:
|
|
line = re.sub (r'(\S)\s+(\S)', r'\1 \2', line)
|
|
|
|
# well, I guess there's some actual content there: return it
|
|
return line
|
|
|
|
# end readline
|
|
|
|
|
|
def readlines (self):
|
|
"""Read and return the list of all logical lines remaining in the
|
|
current file."""
|
|
|
|
lines = []
|
|
while 1:
|
|
line = self.readline()
|
|
if line is None:
|
|
return lines
|
|
lines.append (line)
|
|
|
|
|
|
def unreadline (self, line):
|
|
"""Push 'line' (a string) onto an internal buffer that will be
|
|
checked by future 'readline()' calls. Handy for implementing
|
|
a parser with line-at-a-time lookahead."""
|
|
|
|
self.linebuf.append (line)
|
|
|
|
|
|
if __name__ == "__main__":
|
|
test_data = """# test file
|
|
|
|
line 3 \\
|
|
continues on next line
|
|
"""
|
|
|
|
|
|
# result 1: no fancy options
|
|
result1 = map (lambda x: x + "\n", string.split (test_data, "\n")[0:-1])
|
|
|
|
# result 2: just strip comments
|
|
result2 = ["\n", "\n", "line 3 \\\n", "continues on next line\n"]
|
|
|
|
# result 3: just strip blank lines
|
|
result3 = ["# test file\n", "line 3 \\\n", "continues on next line\n"]
|
|
|
|
# result 4: default, strip comments, blank lines, and trailing whitespace
|
|
result4 = ["line 3 \\", "continues on next line"]
|
|
|
|
# result 5: full processing, strip comments and blanks, plus join lines
|
|
result5 = ["line 3 continues on next line"]
|
|
|
|
def test_input (count, description, file, expected_result):
|
|
result = file.readlines ()
|
|
# result = string.join (result, '')
|
|
if result == expected_result:
|
|
print "ok %d (%s)" % (count, description)
|
|
else:
|
|
print "not ok %d (%s):" % (count, description)
|
|
print "** expected:"
|
|
print expected_result
|
|
print "** received:"
|
|
print result
|
|
|
|
|
|
filename = "test.txt"
|
|
out_file = open (filename, "w")
|
|
out_file.write (test_data)
|
|
out_file.close ()
|
|
|
|
in_file = TextFile (filename, strip_comments=0, skip_blanks=0,
|
|
lstrip_ws=0, rstrip_ws=0)
|
|
test_input (1, "no processing", in_file, result1)
|
|
|
|
in_file = TextFile (filename, strip_comments=1, skip_blanks=0,
|
|
lstrip_ws=0, rstrip_ws=0)
|
|
test_input (2, "strip comments", in_file, result2)
|
|
|
|
in_file = TextFile (filename, strip_comments=0, skip_blanks=1,
|
|
lstrip_ws=0, rstrip_ws=0)
|
|
test_input (3, "strip blanks", in_file, result3)
|
|
|
|
in_file = TextFile (filename)
|
|
test_input (4, "default processing", in_file, result4)
|
|
|
|
in_file = TextFile (filename, strip_comments=1, skip_blanks=1,
|
|
join_lines=1, rstrip_ws=1)
|
|
test_input (5, "full processing", in_file, result5)
|
|
|
|
os.remove (filename)
|
|
|