python_json
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10.4.1 使用 json.dump() 和 json.load()我们来编写一个存储一组数字的简短程序,再编写一个将这些数字读取到内存中的程序。第一个程序将使用 json.dump() 来存储这组数字,而第二个程序将使用 json.load() 。函数 json.dump() 接受两个实参:要存储的数据以及可用于存储数据的文件对象。下面演示了如何使用 json.dump() 来存储数字列表:number_writer.pyimport jsonnumbers = [2, 3, 5, 7, 11, 13]❶❷❸filename = 'numbers.json'with open(filename, 'w') as f_obj:json.dump(numbers, f_obj)Json
import stringimport types## json.py implements a JSON (http://json.org) reader and writer.## Copyright (C) 2005 Patrick D. Logan## Contact mailto:patrickdlogan@stardecisions.com#### This library is free software; you can redistribute it and/or## modify it under the terms of the GNU Lesser General Public## License as published by the Free Software Foundation; either## version 2.1 of the License, or (at your option) any later version.#### This library 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## Lesser General Public License for more details.#### You should have received a copy of the GNU Lesser General Public## License along with this library; if not, write to the Free Software## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USAclass _StringGenerator(object): def __init__(self, string): self.string = string self.index = -1 def peek(self): i = self.index + 1 if i < len(self.string): return self.string[i] else: return None def next(self): self.index += 1 if self.index < len(self.string): return self.string[self.index] else: raise StopIteration def all(self): return self.stringclass WriteException(Exception): passclass ReadException(Exception): passclass JsonReader(object): hex_digits = {'A': 10,'B': 11,'C': 12,'D': 13,'E': 14,'F':15} escapes = {'t':'\t','n':'\n','f':'\f','r':'\r','b':'\b'} def read(self, s): self._generator = _StringGenerator(s) result = self._read() return result def _read(self): self._eatWhitespace() peek = self._peek() if peek is None: raise ReadException, "Nothing to read: '%s'" % self._generator.all() if peek == '{': return self._readObject() elif peek == '[': return self._readArray() elif peek == '"': return self._readString() elif peek == '-' or peek.isdigit(): return self._readNumber() elif peek == 't': return self._readTrue() elif peek == 'f': return self._readFalse() elif peek == 'n': return self._readNull() elif peek == '/': self._readComment() return self._read() else: raise ReadException, "Input is not valid JSON: '%s'" % self._generator.all() def _readTrue(self): self._assertNext('t', "true") self._assertNext('r', "true") self._assertNext('u', "true") self._assertNext('e', "true") return True def _readFalse(self): self._assertNext('f', "false") self._assertNext('a', "false") self._assertNext('l', "false") self._assertNext('s', "false") self._assertNext('e', "false") return False def _readNull(self): self._assertNext('n', "null") self._assertNext('u', "null") self._assertNext('l', "null") self._assertNext('l', "null") return None def _assertNext(self, ch, target): if self._next() != ch: raise ReadException, "Trying to read %s: '%s'" % (target, self._generator.all()) def _readNumber(self): isfloat = False result = self._next() peek = self._peek() while peek is not None and (peek.isdigit() or peek == "."): isfloat = isfloat or peek == "." result = result + self._next() peek = self._peek() try: if isfloat: return float(result) else: return int(result) except ValueError: raise ReadException, "Not a valid JSON number: '%s'" % result def _readString(self): result = "" assert self._next() == '"' try: while self._peek() != '"': ch = self._next() if ch == "\\": ch = self._next() if ch in 'brnft': ch = self.escapes[ch] elif ch == "u": ch4096 = self._next() ch256 = self._next() ch16 = self._next() ch1 = self._next() n = 4096 * self._hexDigitToInt(ch4096) n += 256 * self._hexDigitToInt(ch256) n += 16 * self._hexDigitToInt(ch16) n += self._hexDigitToInt(ch1) ch = unichr(n) elif ch not in '"/\\': raise ReadException, "Not a valid escaped JSON character: '%s' in %s" % (ch, self._generator.all()) result = result + ch except StopIteration: raise ReadException, "Not a valid JSON string: '%s'" % self._generator.all() assert self._next() == '"' return result def _hexDigitToInt(self, ch): try: result = self.hex_digits[ch.upper()] except KeyError: try: result = int(ch) except ValueError: raise ReadException, "The character %s is not a hex digit." % ch return result def _readComment(self): assert self._next() == "/" second = self._next() if second == "/": self._readDoubleSolidusComment() elif second == '*': self._readCStyleComment() else: raise ReadException, "Not a valid JSON comment: %s" % self._generator.all() def _readCStyleComment(self): try: done = False while not done: ch = self._next() done = (ch == "*" and self._peek() == "/") if not done and ch == "/" and self._peek() == "*": raise ReadException, "Not a valid JSON comment: %s, '/*' cannot be embedded in the comment." % self._generator.all() self._next() except StopIteration: raise ReadException, "Not a valid JSON comment: %s, expected */" % self._generator.all() def _readDoubleSolidusComment(self): try: ch = self._next() while ch != "\r" and ch != "\n": ch = self._next() except StopIteration: pass def _readArray(self): result = [] assert self._next() == '[' done = self._peek() == ']' while not done: item = self._read() result.append(item) self._eatWhitespace() done = self._peek() == ']' if not done: ch = self._next() if ch != ",": raise ReadException, "Not a valid JSON array: '%s' due to: '%s'" % (self._generator.all(), ch) assert ']' == self._next() return result def _readObject(self): result = {} assert self._next() == '{' done = self._peek() == '}' while not done: key = self._read() if type(key) is not types.StringType: raise ReadException, "Not a valid JSON object key (should be a string): %s" % key self._eatWhitespace() ch = self._next() if ch != ":": raise ReadException, "Not a valid JSON object: '%s' due to: '%s'" % (self._generator.all(), ch) self._eatWhitespace() val = self._read() result[key] = val self._eatWhitespace() done = self._peek() == '}' if not done: ch = self._next() if ch != ",": raise ReadException, "Not a valid JSON array: '%s' due to: '%s'" % (self._generator.all(), ch) assert self._next() == "}" return result def _eatWhitespace(self): p = self._peek() while p is not None and p in string.whitespace or p == '/': if p == '/': self._readComment() else: self._next() p = self._peek() def _peek(self): return self._generator.peek() def _next(self): return self._generator.next()class JsonWriter(object): def _append(self, s): self._results.append(s) def write(self, obj, escaped_forward_slash=False): self._escaped_forward_slash = escaped_forward_slash self._results = [] self._write(obj) return "".join(self._results) def _write(self, obj): ty = type(obj) if ty is types.DictType: n = len(obj) self._append("{") for k, v in obj.items(): self._write(k) self._append(":") self._write(v) n = n - 1 if n > 0: self._append(",") self._append("}") elif ty is types.ListType or ty is types.TupleType: n = len(obj) self._append("[") for item in obj: self._write(item) n = n - 1 if n > 0: self._append(",") self._append("]") elif ty is types.StringType or ty is types.UnicodeType: self._append('"') obj = obj.replace('\\', r'\\') if self._escaped_forward_slash: obj = obj.replace('/', r'\/') obj = obj.replace('"', r'\"') obj = obj.replace('\b', r'\b') obj = obj.replace('\f', r'\f') obj = obj.replace('\n', r'\n') obj = obj.replace('\r', r'\r') obj = obj.replace('\t', r'\t') self._append(obj) self._append('"') elif ty is types.IntType or ty is types.LongType: self._append(str(obj)) elif ty is types.FloatType: self._append("%f" % obj) elif obj is True: self._append("true") elif obj is False: self._append("false") elif obj is None: self._append("null") else: raise WriteException, "Cannot write in JSON: %s" % repr(obj)def write(obj, escaped_forward_slash=False): return JsonWriter().write(obj, escaped_forward_slash)def read(s): return JsonReader().read(s)minijson
################################################################################## minjson.py implements JSON reading and writing in python.## Copyright (c) 2005 Jim Washington and Contributors.#### This library is free software; you can redistribute it and/or## modify it under the terms of the GNU Lesser General Public## License as published by the Free Software Foundation; either## version 2.1 of the License, or (at your option) any later version.#### This library 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## Lesser General Public License for more details.=#### You should have received a copy of the GNU Lesser General Public## License along with this library; if not, write to the Free Software## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA################################################################################# minjson.py# use python's parser to read minimal javascript objects.# str's objects and fixes the text to write javascript.# Thanks to Patrick Logan for starting the json-py project and making so many# good test cases.# Jim Washington 7 Aug 2005.from re import compile, sub, search, DOTALL# set to true if transmission size is much more important than speed# only affects writing, and makes a minimal difference in output size.alwaysStripWhiteSpace = False# add to this string if you wish to exclude additional math operators# from reading.badOperators = '*'################################## read JSON object ##################################slashstarcomment = compile(r'/\*.*?\*/',DOTALL)doubleslashcomment = compile(r'//.*\n')def _Read(aString): """Use eval in a 'safe' way to turn javascript expression into a python expression. Allow only True, False, and None in global __builtins__, and since those map as true, false, null in javascript, pass those as locals """ try: result = eval(aString, {"__builtins__":{'True':True,'False':False,'None':None}}, {'null':None,'true':True,'false':False}) except NameError: raise ReadException, \ "Strings must be quoted. Could not read '%s'." % aString except SyntaxError: raise ReadException, \ "Syntax error. Could not read '%s'." % aString return result# badOperators is defined at the top of the module# generate the regexes for math detectionregexes = {}for operator in badOperators: if operator in '+*': # '+' and '*' need to be escaped with \ in re regexes[operator,'numeric operation'] \ = compile(r"\d*\s*\%s|\%s\s*\d*" % (operator, operator)) else: regexes[operator,'numeric operation'] \ = compile(r"\d*\s*%s|%s\s*\d*" % (operator, operator))def _getStringState(aSequence): """return the list of required quote closures if the end of aString needs them to close quotes. """ state = [] for k in aSequence: if k in ['"',"'"]: if state and k == state[-1]: state.pop() else: state.append(k) return statedef _sanityCheckMath(aString): """just need to check that, if there is a math operator in the client's JSON, it is inside a quoted string. This is mainly to keep client from successfully sending 'D0S'*9**9**9**9... Return True if OK, False otherwise """ for operator in badOperators: #first check, is it a possible math operation? if regexes[(operator,'numeric operation')].search(aString) is not None: # OK. possible math operation. get the operator's locations getlocs = regexes[(operator,'numeric operation')].finditer(aString) locs = [item.span() for item in getlocs] halfStrLen = len(aString) / 2 #fortunately, this should be rare for loc in locs: exprStart = loc[0] exprEnd = loc[1] # We only need to know the char is within open quote # status. if exprStart <= halfStrLen: teststr = aString[:exprStart] else: teststr = list(aString[exprEnd+1:]) teststr.reverse() if not _getStringState(teststr): return False return Truedef safeRead(aString): """turn the js into happier python and check for bad operations before sending it to the interpreter """ # get rid of trailing null. Konqueror appends this, and the python # interpreter balks when it is there. CHR0 = chr(0) while aString.endswith(CHR0): aString = aString[:-1] # strip leading and trailing whitespace aString = aString.strip() # zap /* ... */ comments aString = slashstarcomment.sub('',aString) # zap // comments aString = doubleslashcomment.sub('',aString) # here, we only check for the * operator as a DOS problem by default; # additional operators may be excluded by editing badOperators # at the top of the module if _sanityCheckMath(aString): return _Read(aString) else: raise ReadException, 'Unacceptable JSON expression: %s' % aStringread = safeRead################################## write object as JSON ###################################alwaysStripWhiteSpace is defined at the top of the moduletfnTuple = (('True','true'),('False','false'),('None','null'),)def _replaceTrueFalseNone(aString): """replace True, False, and None with javascript counterparts""" for k in tfnTuple: if k[0] in aString: aString = aString.replace(k[0],k[1]) return aStringdef _handleCode(subStr,stripWhiteSpace): """replace True, False, and None with javascript counterparts if appropriate, remove unicode u's, fix long L's, make tuples lists, and strip white space if requested """ if 'e' in subStr: #True, False, and None have 'e' in them. :) subStr = (_replaceTrueFalseNone(subStr)) if stripWhiteSpace: # re.sub might do a better job, but takes longer. # Spaces are the majority of the whitespace, anyway... subStr = subStr.replace(' ','') if subStr[-1] in "uU": #remove unicode u's subStr = subStr[:-1] if "L" in subStr: #remove Ls from long ints subStr = subStr.replace("L",'') #do tuples as lists if "(" in subStr: subStr = subStr.replace("(",'[') if ")" in subStr: subStr = subStr.replace(")",']') return subStr# re for a double-quoted string that has a single-quote in it# but no double-quotes and python punctuation after:redoublequotedstring = compile(r'"[^"]*\'[^"]*"[,\]\}:\)]')escapedSingleQuote = r"\'"escapedDoubleQuote = r'\"'def doQuotesSwapping(aString): """rewrite doublequoted strings with single quotes as singlequoted strings with escaped single quotes""" s = [] foundlocs = redoublequotedstring.finditer(aString) prevend = 0 for loc in foundlocs: start,end = loc.span() s.append(aString[prevend:start]) tempstr = aString[start:end] endchar = tempstr[-1] ts1 = tempstr[1:-2] ts1 = ts1.replace("'",escapedSingleQuote) ts1 = "'%s'%s" % (ts1,endchar) s.append(ts1) prevend = end s.append(aString[prevend:]) return ''.join(s)def _pyexpr2jsexpr(aString, stripWhiteSpace): """Take advantage of python's formatting of string representations of objects. Python always uses "'" to delimit strings. Except it doesn't when there is ' in the string. Fix that, then, if we split on that delimiter, we have a list that alternates non-string text with string text. Since string text is already properly escaped, we only need to replace True, False, and None in non-string text and remove any unicode 'u's preceding string values. if stripWhiteSpace is True, remove spaces, etc from the non-string text. """ inSingleQuote = False inDoubleQuote = False #python will quote with " when there is a ' in the string, #so fix that first if redoublequotedstring.search(aString): aString = doQuotesSwapping(aString) marker = None if escapedSingleQuote in aString: #replace escaped single quotes with a marker marker = markerBase = '|' markerCount = 1 while marker in aString: #if the marker is already there, make it different markerCount += 1 marker = markerBase * markerCount aString = aString.replace(escapedSingleQuote,marker) #escape double-quotes aString = aString.replace('"',escapedDoubleQuote) #split the string on the real single-quotes splitStr = aString.split("'") outList = [] alt = True for subStr in splitStr: #if alt is True, non-string; do replacements if alt: subStr = _handleCode(subStr,stripWhiteSpace) outList.append(subStr) alt = not alt result = '"'.join(outList) if marker: #put the escaped single-quotes back as "'" result = result.replace(marker,"'") return resultdef write(obj, encoding="utf-8",stripWhiteSpace=alwaysStripWhiteSpace): """Represent the object as a string. Do any necessary fix-ups with pyexpr2jsexpr""" try: #not really sure encode does anything here aString = str(obj).encode(encoding) except UnicodeEncodeError: aString = obj.encode(encoding) if isinstance(obj,basestring): if '"' in aString: aString = aString.replace(escapedDoubleQuote,'"') result = '"%s"' % aString.replace('"',escapedDoubleQuote) else: result = '"%s"' % aString else: result = _pyexpr2jsexpr(aString,stripWhiteSpace).encode(encoding) return resultclass ReadException(Exception): passclass WriteException(Exception): pass 0 0
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