Okay, I got fed up with there not being any (obvious) good examples of how to do bash-like brace expansion in Python, so I wrote it myself. Here it is for all to enjoy!
If anyone has any better solutions or any other examples of how to do this, I'd be glad to hear from them. #~ BraceExpand.py - Bash-like brace expansion in Python #~ Copyright (C) 2009 <peter.wal...@gmail.com> #~ This program is free software: you can redistribute it and/or modify #~ it under the terms of the GNU Affero General Public License as #~ published by the Free Software Foundation, either version 3 of the #~ License, or (at your option) any later version. #~ This program is distributed in the hope that it will be useful, #~ but WITHOUT ANY WARRANTY; without even the implied warranty of #~ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the #~ GNU Affero General Public License for more details. #~ You should have received a copy of the GNU Affero General Public License #~ along with this program. If not, see <http://www.gnu.org/licenses/ >. import re from itertools import imap class NoBraces(Exception): pass def BraceExpand(text, ordering = []): """Recursively brace expand text in a bash-like fashion. See 'man 2 bash' under the heading 'Brace Expansion' Example: "/data/file{1..10}.root" expands to file1.root ... file9.root Ordering allows changing the order of iteration. The rules for this are a little complicated. Ordering is a list of boolean values. If it is possible to expand the postamble, the first value from the list is removed, and used to determine whether the postamble should be iterated over before iterating over the amble. The list is then passed down recursively to the next Brace. What does this code do? It is simpler than it looks. There are three main steps: 1) Split the string into three parts, consisting of pre-amble, amble and post-amble. (This requires keeping track of nested {}'s.) 2) In the amble, figure out which commas are not stuck in {}'s, and split the string by those commas. 3) For each part of this split string, Add together the pre- amble, the string and the post-amble. Call BraceExpand() on this string to deal with nested braces and any expansion required in the postamble Other things this code does which make it look more complicated: * Expand ranges along the lines of {1..10} * Allow for re-arranging the order of iteration Todo/Not Implemented: * Escaping/quoting Example C implementation from bash (inspiration for this): http://www.oldlinux.org/Linux.old/bin/old/bash-1.11/braces.c """ def FindMatchedBraces(text, position = -1): "Search for nested start and end brace in text starting from position" braceDepth = 0 nextClose = -1 first = True # Search for a { # is it closer than the nearest } ? # Yes : increase brace depth # No : decrease brace depth # When we reach braceDepth == 0, we have found our close brace while braceDepth or first: nextOpen = text.find("{", position+1) nextClose = text.find("}", position+1) if first and nextOpen >= 0: startBrace = nextOpen first = False if nextOpen < nextClose and nextOpen >= 0: braceDepth += 1 position = nextOpen elif nextClose >= 0: braceDepth -= 1 position = nextClose else: raise NoBraces() return startBrace, position try: start, end = FindMatchedBraces(text) except NoBraces: # There are no braces! Nothing to expand! return [text] # Split the text into three bits, '{pre,,post}amble'. The 'pre' is anything # before expansion, the '' is the bit that needs expanding and gluing to # the pre and the post. After gluing together, we can recursively expand # again preamble = text[:start] amble = text[start+1:end] postamble = text[end+1:] def BareCommaSearcher(amble): "Search for commas which are not encapsulated in {}" haveBraces = True try: start, end = FindMatchedBraces(amble) except NoBraces: haveBraces = False position = -1 while True: position = amble.find(",", position+1) if position < 0: # We didn't find any comma after 'position', finish searching. break if haveBraces and start < position < end: # We're inside some braces, skip to the end of them, find the # next set. position = end haveBraces = True try: start, end = FindMatchedBraces(amble, position) except NoBraces: haveBraces = False continue yield position # Reached the end of the string. (Conveniently "text"[pos:None] is the # same as "text"[pos:] yield None parts = [] rangeMatcher = re.compile(r"^(\d+)..(\d+)$") # Find each segment of the amble, splitting by 'bare' commas position = 0 for commaPos in BareCommaSearcher(amble): # Get a bit between bare commas part = amble[position:commaPos] # Found a matched range, expand it! matchedRange = rangeMatcher.match(part) if matchedRange: matchedIndices = map(int, matchedRange.groups()) parts.extend(imap(str,xrange(*matchedIndices))) else: parts.append(part) if not commaPos: # Avoid None + 1 at the end of iteration break position = commaPos + 1 # Is the postamble expandable? (Does it contain braces?) postambleExpandable = True try: start, end = FindMatchedBraces(postamble) except NoBraces: postambleExpandable = False # Check to see if we should iterate over postamble first, also sort out # iteration ordering postambleFirst = ordering thisPostambleFirst = False if postambleExpandable and postambleFirst: postambleFirst = list(postambleFirst) thisPostambleFirst = postambleFirst.pop(0) result = [] if postambleExpandable and thisPostambleFirst: # Iterate of expanded postamble first for postpart in BraceExpand(postamble): for part in parts: part = "".join([preamble, part, postpart]) result.extend(BraceExpand(part, postambleFirst)) else: for part in parts: part = "".join([preamble, part, postamble]) result.extend(BraceExpand(part, postambleFirst)) return result if __name__ == "__main__": from pprint import pprint pprint(BraceExpand("electron_{n,{pt,eta,phi}[{1,2}]}", ordering = [True])) #~ pprint(BraceExpand("Myfile{1,3..10}.root")) #~ pprint(BraceExpand("{pre,,post}amble")) #~ pprint(BraceExpand("amble{a,b,}}")) -- http://mail.python.org/mailman/listinfo/python-list
