在java 編程中，很多配置文件用鍵值對的方式存儲在 PRoperties 文件中，可以讀取，修改。而且在java 中有 java.util.Properties 這個類，可以很方便的處理properties 文件， 在python 中雖然也有讀取配置文件的類ConfigParser, 但如果習慣java 編程的人估計更喜歡下面這個用python 實現的讀取 properties 文件的類：
"""A Python replacement for java.util.Properties classThis is modelled as closely as possible to the Java original. """import sys,osimport reimport timeclass IllegalArgumentException(Exception): def __init__(self, lineno, msg): self.lineno = lineno self.msg = msg def __str__(self): s='Exception at line number %d => %s' % (self.lineno, self.msg) return sclass Properties(object): """ A Python replacement for java.util.Properties """ def __init__(self, props=None): # Note: We don't take a default properties object # as argument yet # Dictionary of properties. self._props = {} # Dictionary of properties with 'pristine' keys # This is used for dumping the properties to a file # using the 'store' method self._origprops = {} # Dictionary mapping keys from property # dictionary to pristine dictionary self._keymap = {} self.othercharre = re.compile(r'(?<!//)(/s*/=)|(?<!//)(/s*/:)') self.othercharre2 = re.compile(r'(/s*/=)|(/s*/:)') self.bspacere = re.compile(r'//(?!/s$)') def __str__(self): s='{' for key,value in self._props.items(): s = ''.join((s,key,'=',value,', ')) s=''.join((s[:-2],'}')) return s def __parse(self, lines): """ Parse a list of lines and create an internal property dictionary """ # Every line in the file must consist of either a comment # or a key-value pair. A key-value pair is a line consisting # of a key which is a combination of non-white space characters # The separator character between key-value pairs is a '=', # ':' or a whitespace character not including the newline. # If the '=' or ':' characters are found, in the line, even # keys containing whitespace chars are allowed. # A line with only a key according to the rules above is also # fine. In such case, the value is considered as the empty string. # In order to include characters '=' or ':' in a key or value, # they have to be properly escaped using the backslash character. # Some examples of valid key-value pairs: # # key value # key=value # key:value # key value1,value2,value3 # key value1,value2,value3 / # value4, value5 # key # This key= this value # key = value1 value2 value3 # Any line that starts with a '#' is considerered a comment # and skipped. Also any trailing or preceding whitespaces # are removed from the key/value. # This is a line parser. It parses the # contents like by line. lineno=0 i = iter(lines) for line in i: lineno += 1 line = line.strip() # Skip null lines if not line: continue # Skip lines which are comments if line[0] == '#': continue # Some flags escaped=False # Position of first separation char sepidx = -1 # A flag for performing wspace re check flag = 0 # Check for valid space separation # First obtain the max index to which we # can search. m = self.othercharre.search(line) if m: first, last = m.span() start, end = 0, first flag = 1 wspacere = re.compile(r'(?<![///=/:])(/s)') else: if self.othercharre2.search(line): # Check if either '=' or ':' is present # in the line. If they are then it means # they are preceded by a backslash. # This means, we need to modify the # wspacere a bit, not to look for # : or = characters. wspacere = re.compile(r'(?<![//])(/s)') start, end = 0, len(line) m2 = wspacere.search(line, start, end) if m2: # print 'Space match=>',line # Means we need to split by space. first, last = m2.span() sepidx = first elif m: # print 'Other match=>',line # No matching wspace char found, need # to split by either '=' or ':' first, last = m.span() sepidx = last - 1 # print line[sepidx] # If the last character is a backslash # it has to be preceded by a space in which # case the next line is read as part of the # same property while line[-1] == '//': # Read next line nextline = i.next() nextline = nextline.strip() lineno += 1 # This line will become part of the value line = line[:-1] + nextline # Now split to key,value according to separation char if sepidx != -1: key, value = line[:sepidx], line[sepidx+1:] else: key,value = line,'' self.processPair(key, value) def processPair(self, key, value): """ Process a (key, value) pair """ oldkey = key oldvalue = value # Create key intelligently keyparts = self.bspacere.split(key) # print keyparts strippable = False lastpart = keyparts[-1] if lastpart.find('// ') != -1: keyparts[-1] = lastpart.replace('//','') # If no backspace is found at the end, but empty # space is found, strip it elif lastpart and lastpart[-1] == ' ': strippable = True key = ''.join(keyparts) if strippable: key = key.strip() oldkey = oldkey.strip() oldvalue = self.unescape(oldvalue) value = self.unescape(value) self._props[key] = value.strip() # Check if an entry exists in pristine keys if self._keymap.has_key(key): oldkey = self._keymap.get(key) self._origprops[oldkey] = oldvalue.strip() else: self._origprops[oldkey] = oldvalue.strip() # Store entry in keymap self._keymap[key] = oldkey def escape(self, value): # Java escapes the '=' and ':' in the value # string with backslashes in the store method. # So let us do the same. newvalue = value.replace(':','/:') newvalue = newvalue.replace('=','/=') return newvalue def unescape(self, value): # Reverse of escape newvalue = value.replace('/:',':') newvalue = newvalue.replace('/=','=') return newvalue def load(self, stream): """ Load properties from an open file stream """ # For the time being only accept file input streams if type(stream) is not file: raise TypeError,'Argument should be a file object!' # Check for the opened mode if stream.mode != 'r': raise ValueError,'Stream should be opened in read-only mode!' try: lines = stream.readlines() self.__parse(lines) except IOError, e: raise def getProperty(self, key): """ Return a property for the given key """ return self._props.get(key,'') def setProperty(self, key, value): """ Set the property for the given key """ if type(key) is str and type(value) is str: self.processPair(key, value) else: raise TypeError,'both key and value should be strings!' def propertyNames(self): """ Return an iterator over all the keys of the property dictionary, i.e the names of the properties """ return self._props.keys() def list(self, out=sys.stdout): """ Prints a listing of the properties to the stream 'out' which defaults to the standard output """ out.write('-- listing properties --/n') for key,value in self._props.items(): out.write(''.join((key,'=',value,'/n'))) def store(self, out, header=""): """ Write the properties list to the stream 'out' along with the optional 'header' """ if out.mode[0] != 'w': raise ValueError,'Steam should be opened in write mode!' try: out.write(''.join(('#',header,'/n'))) # Write timestamp tstamp = time.strftime('%a %b %d %H:%M:%S %Z %Y', time.localtime()) out.write(''.join(('#',tstamp,'/n'))) # Write properties from the pristine dictionary for prop, val in self._origprops.items(): out.write(''.join((prop,'=',self.escape(val),'/n'))) out.close() except IOError, e: raise def getPropertyDict(self): return self._props def __getitem__(self, name): """ To support direct dictionary like access """ return self.getProperty(name) def __setitem__(self, name, value): """ To support direct dictionary like access """ self.setProperty(name, value) def __getattr__(self, name): """ For attributes not found in self, redirect to the properties dictionary """ try: return self.__dict__[name] except KeyError: if hasattr(self._props,name): return getattr(self._props, name)if __name__=="__main__": p = Properties() p.load(open('test2.properties')) p.list() print p print p.items() print p['name3'] p['name3'] = 'changed = value' print p['name3'] p['new key'] = 'new value' p.store(open('test2.properties','w'))當然，測試這個類你需要在程序目錄下簡歷test2.properties 文件。才可以看到效果，基本可以達到用python 讀寫 properties 文件的效果.
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