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textwrap now processes text chucks at O(n) speed instead of O(n**2).

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Patch #1209527 (Contributed by Connelly).
This commit is contained in:
Raymond Hettinger 2005-07-15 06:53:35 +00:00
parent d5d469d3d1
commit 8bfa8935ea
2 changed files with 16 additions and 9 deletions
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22
Lib/textwrap.py
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@ -161,7 +161,7 @@ class TextWrapper:
else: else:
i += 1 i += 1
def _handle_long_word(self, chunks, cur_line, cur_len, width): def _handle_long_word(self, reversed_chunks, cur_line, cur_len, width):
"""_handle_long_word(chunks : [string], """_handle_long_word(chunks : [string],
cur_line : [string], cur_line : [string],
cur_len : int, width : int) cur_len : int, width : int)
@ -174,14 +174,14 @@ class TextWrapper:
# If we're allowed to break long words, then do so: put as much # If we're allowed to break long words, then do so: put as much
# of the next chunk onto the current line as will fit. # of the next chunk onto the current line as will fit.
if self.break_long_words: if self.break_long_words:
cur_line.append(chunks[0][0:space_left]) cur_line.append(reversed_chunks[-1][:space_left])
chunks[0] = chunks[0][space_left:] reversed_chunks[-1] = reversed_chunks[-1][space_left:]
# Otherwise, we have to preserve the long word intact. Only add # Otherwise, we have to preserve the long word intact. Only add
# it to the current line if there's nothing already there -- # it to the current line if there's nothing already there --
# that minimizes how much we violate the width constraint. # that minimizes how much we violate the width constraint.
elif not cur_line: elif not cur_line:
cur_line.append(chunks.pop(0)) cur_line.append(reversed_chunks.pop())
# If we're not allowed to break long words, and there's already # If we're not allowed to break long words, and there's already
# text on the current line, do nothing. Next time through the # text on the current line, do nothing. Next time through the
@ -206,6 +206,10 @@ class TextWrapper:
if self.width <= 0: if self.width <= 0:
raise ValueError("invalid width %r (must be > 0)" % self.width) raise ValueError("invalid width %r (must be > 0)" % self.width)
# Arrange in reverse order so items can be efficiently popped
# from a stack of chucks.
chunks.reverse()
while chunks: while chunks:
# Start the list of chunks that will make up the current line. # Start the list of chunks that will make up the current line.
@ -224,15 +228,15 @@ class TextWrapper:
# First chunk on line is whitespace -- drop it, unless this # First chunk on line is whitespace -- drop it, unless this
# is the very beginning of the text (ie. no lines started yet). # is the very beginning of the text (ie. no lines started yet).
if chunks[0].strip() == '' and lines: if chunks[-1].strip() == '' and lines:
del chunks[0] del chunks[-1]
while chunks: while chunks:
l = len(chunks[0]) l = len(chunks[-1])
# Can at least squeeze this chunk onto the current line. # Can at least squeeze this chunk onto the current line.
if cur_len + l <= width: if cur_len + l <= width:
cur_line.append(chunks.pop(0)) cur_line.append(chunks.pop())
cur_len += l cur_len += l
# Nope, this line is full. # Nope, this line is full.
@ -241,7 +245,7 @@ class TextWrapper:
# The current line is full, and the next chunk is too big to # The current line is full, and the next chunk is too big to
# fit on *any* line (not just this one). # fit on *any* line (not just this one).
if chunks and len(chunks[0]) > width: if chunks and len(chunks[-1]) > width:
self._handle_long_word(chunks, cur_line, cur_len, width) self._handle_long_word(chunks, cur_line, cur_len, width)
# If the last chunk on this line is all whitespace, drop it. # If the last chunk on this line is all whitespace, drop it.

3
Misc/NEWS
View File

@ -168,6 +168,9 @@ Extension Modules
Library Library
------- -------
- textwrap now processes text chucks at O(n) speed instead of O(n**2).
Patch #1209527 (Contributed by Connelly).
- urllib2 has now an attribute 'httpresponses' mapping from HTTP status code - urllib2 has now an attribute 'httpresponses' mapping from HTTP status code
to W3C name (404 -> 'Not Found'). RFE #1216944. to W3C name (404 -> 'Not Found'). RFE #1216944.