用python 实现 java.util.Properties 类的一些基本操作
By:Roy.LiuLast updated:2014-03-09
在java 编程中,很多配置文件用键值对的方式存储在 properties 文件中,可以读取,修改。而且在java 中有 java.util.Properties 这个类,可以很方便的处理properties 文件, 在python 中虽然也有读取配置文件的类ConfigParser, 但如果习惯java 编程的人估计更喜欢下面这个用python 实现的读取 properties 文件的类:
当然,测试这个类你需要在程序目录下简历test2.properties 文件。才可以看到效果,基本可以达到用python 读写 properties 文件的效果.
""" A Python replacement for java.util.Properties class This is modelled as closely as possible to the Java original. """ import sys,os import re import time class 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 s class 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'(?',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'))
当然,测试这个类你需要在程序目录下简历test2.properties 文件。才可以看到效果,基本可以达到用python 读写 properties 文件的效果.
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