Python装饰器使用实例：验证参数合法性

# -*- coding: UTF-8 -*- '''@summary: 验证器该模块提供了一个装饰器用于验证参数是否合法，使用方法为： from validator import validParam, nullOk, multiType @validParam(i=int)def foo(i):  return i+1 编写验证器： 1. 仅验证类型：@validParam(type, ...)例如：检查第一个位置的参数是否为int类型：@validParam(int)检查名为x的参数是否为int类型：@validParam(x=int) 验证多个参数：@validParam(int, int)指定参数名验证：@validParam(int, s=str) 针对*和**参数编写的验证器将验证这些参数实际包含的每个元素：@validParam(varargs=int)def foo(*varargs): pass @validParam(kws=int)def foo7(s, **kws): pass 2. 带有条件的验证：@validParam((type, condition), ...)其中，condition是一个表达式字符串，使用x引用待验证的对象；根据bool(表达式的值)判断是否通过验证，若计算表达式时抛出异常，视为失败。例如：验证一个10到20之间的整数：@validParam(i=(int, '10<x<20'))验证一个长度小于20的字符串：@validParam(s=(str, 'len(x)<20'))验证一个年龄小于20的学生：@validParam(stu=(Student, 'x.age<20')) 另外，如果类型是字符串，condition还可以使用斜杠开头和结尾表示正则表达式匹配。验证一个由数字组成的字符串：@validParam(s=(str, '/^/d*$/')) 3. 以上验证方式默认为当值是None时验证失败。如果None是合法的参数，可以使用nullOk()。nullOk()接受一个验证条件作为参数。例如：@validParam(i=nullOk(int))@validParam(i=nullOk((int, '10<x<20')))也可以简写为：@validParam(i=nullOk(int, '10<x<20')) 4. 如果参数有多个合法的类型，可以使用multiType()。multiType()可接受多个参数，每个参数都是一个验证条件。例如：@validParam(s=multiType(int, str))@validParam(s=multiType((int, 'x>20'), nullOk(str, '/^/d+$/'))) 5. 如果有更复杂的验证需求，还可以编写一个函数作为验证函数传入。这个函数接收待验证的对象作为参数，根据bool(返回值)判断是否通过验证，抛出异常视为失败。例如：def validFunction(x):  return isinstance(x, int) and x>0@validParam(i=validFunction)def foo(i): pass 这个验证函数等价于：@validParam(i=(int, 'x>0'))def foo(i): pass  @author: HUXI@since: 2011-3-22@change: ''' import inspectimport re class ValidateException(Exception): pass  def validParam(*varargs, **keywords):  '''验证参数的装饰器。'''     varargs = map(_toStardardCondition, varargs)  keywords = dict((k, _toStardardCondition(keywords[k]))          for k in keywords)     def generator(func):    args, varargname, kwname = inspect.getargspec(func)[:3]    dctValidator = _getcallargs(args, varargname, kwname,                  varargs, keywords)         def wrapper(*callvarargs, **callkeywords):      dctCallArgs = _getcallargs(args, varargname, kwname,                    callvarargs, callkeywords)             k, item = None, None      try:        for k in dctValidator:          if k == varargname:            for item in dctCallArgs[k]:              assert dctValidator[k](item)          elif k == kwname:            for item in dctCallArgs[k].values():              assert dctValidator[k](item)          else:            item = dctCallArgs[k]            assert dctValidator[k](item)      except:        raise ValidateException,/            ('%s() parameter validation fails, param: %s, value: %s(%s)'            % (func.func_name, k, item, item.__class__.__name__))             return func(*callvarargs, **callkeywords)         wrapper = _wrapps(wrapper, func)    return wrapper     return generator  def _toStardardCondition(condition):  '''将各种格式的检查条件转换为检查函数'''     if inspect.isclass(condition):    return lambda x: isinstance(x, condition)     if isinstance(condition, (tuple, list)):    cls, condition = condition[:2]    if condition is None:      return _toStardardCondition(cls)         if cls in (str, unicode) and condition[0] == condition[-1] == '/':      return lambda x: (isinstance(x, cls)               and re.match(condition[1:-1], x) is not None)         return lambda x: isinstance(x, cls) and eval(condition)     return condition  def nullOk(cls, condition=None):  '''这个函数指定的检查条件可以接受None值'''     return lambda x: x is None or _toStardardCondition((cls, condition))(x)  def multiType(*conditions):  '''这个函数指定的检查条件只需要有一个通过'''     lstValidator = map(_toStardardCondition, conditions)  def validate(x):    for v in lstValidator:      if v(x):        return True  return validate  def _getcallargs(args, varargname, kwname, varargs, keywords):  '''获取调用时的各参数名-值的字典'''     dctArgs = {}  varargs = tuple(varargs)  keywords = dict(keywords)     argcount = len(args)  varcount = len(varargs)  callvarargs = None     if argcount <= varcount:    for n, argname in enumerate(args):      dctArgs[argname] = varargs[n]         callvarargs = varargs[-(varcount-argcount):]     else:    for n, var in enumerate(varargs):      dctArgs[args[n]] = var         for argname in args[-(argcount-varcount):]:      if argname in keywords:        dctArgs[argname] = keywords.pop(argname)         callvarargs = ()     if varargname is not None:    dctArgs[varargname] = callvarargs     if kwname is not None:    dctArgs[kwname] = keywords     dctArgs.update(keywords)  return dctArgs  def _wrapps(wrapper, wrapped):  '''复制元数据'''     for attr in ('__module__', '__name__', '__doc__'):    setattr(wrapper, attr, getattr(wrapped, attr))  for attr in ('__dict__',):    getattr(wrapper, attr).update(getattr(wrapped, attr, {}))     return wrapper  #===============================================================================# 测试#===============================================================================  def _unittest(func, *cases):  for case in cases:    _functest(func, *case)    def _functest(func, isCkPass, *args, **kws):  if isCkPass:    func(*args, **kws)  else:    try:      func(*args, **kws)      assert False    except ValidateException:      pass def _test1_simple():  #检查第一个位置的参数是否为int类型：  @validParam(int)  def foo1(i): pass  _unittest(foo1,        (True, 1),        (False, 's'),        (False, None))   #检查名为x的参数是否为int类型：  @validParam(x=int)  def foo2(s, x): pass  _unittest(foo2,        (True, 1, 2),        (False, 's', 's'))     #验证多个参数：  @validParam(int, int)  def foo3(s, x): pass  _unittest(foo3,        (True, 1, 2),        (False, 's', 2))     #指定参数名验证：  @validParam(int, s=str)  def foo4(i, s): pass  _unittest(foo4,        (True, 1, 'a'),        (False, 's', 1))     #针对*和**参数编写的验证器将验证这些参数包含的每个元素：  @validParam(varargs=int)  def foo5(*varargs): pass  _unittest(foo5,       (True, 1, 2, 3, 4, 5),       (False, 'a', 1))     @validParam(kws=int)  def foo6(**kws): pass  _functest(foo6, True, a=1, b=2)  _functest(foo6, False, a='a', b=2)     @validParam(kws=int)  def foo7(s, **kws): pass  _functest(foo7, True, s='a', a=1, b=2)  def _test2_condition():  #验证一个10到20之间的整数：  @validParam(i=(int, '10<x<20'))  def foo1(x, i): pass  _unittest(foo1,        (True, 1, 11),        (False, 1, 'a'),        (False, 1, 1))     #验证一个长度小于20的字符串：  @validParam(s=(str, 'len(x)<20'))  def foo2(a, s): pass  _unittest(foo2,        (True, 1, 'a'),        (False, 1, 1),        (False, 1, 'a'*20))     #验证一个年龄小于20的学生：  class Student(object):    def __init__(self, age): self.age=age     @validParam(stu=(Student, 'x.age<20'))  def foo3(stu): pass  _unittest(foo3,        (True, Student(18)),        (False, 1),        (False, Student(20)))     #验证一个由数字组成的字符串：  @validParam(s=(str, r'/^/d*$/'))  def foo4(s): pass  _unittest(foo4,        (True, '1234'),        (False, 1),        (False, 'a1234'))  def _test3_nullok():  @validParam(i=nullOk(int))  def foo1(i): pass  _unittest(foo1,        (True, 1),        (False, 'a'),        (True, None))     @validParam(i=nullOk(int, '10<x<20'))  def foo2(i): pass  _unittest(foo2,        (True, 11),        (False, 'a'),        (True, None),        (False, 1))  def _test4_multitype():  @validParam(s=multiType(int, str))  def foo1(s): pass  _unittest(foo1,        (True, 1),       (True, 'a'),       (False, None),       (False, 1.1))     @validParam(s=multiType((int, 'x>20'), nullOk(str, '/^/d+$/')))  def foo2(s): pass  _unittest(foo2,        (False, 1),       (False, 'a'),       (True, None),       (False, 1.1),       (True, 21),       (True, '21')) def _main():  d = globals()  from types import FunctionType  print  for f in d:    if f.startswith('_test'):      f = d[f]      if isinstance(f, FunctionType):        f() if __name__ == '__main__':  _main()