以下代码：
class ParentModel(models.Model):
pass
class ChildA(ChildB):
pass
class ChildB(ParentModel):
pass
显然信息失败了。
NameError：名称“ChildB”未定义
有没有解决这个问题，而没有实际重新排序类定义？ （代码是自动生成的，大约45K行，类的顺序是随机的。）
答案 0 :(得分：0)
完美主义者视线远离!! 这是一种解决方法（黑客）;解决方案是解决不正确的声明顺序。
警告：这非常愚蠢。
概念：
想象一下任何东西都可以存在的命名空间。字面上任何被问到的东西。通常不是最聪明的事情，但无序声明也不聪明，为什么不呢？
无序类的关键问题是依赖类是在依赖类（基类）之前定义的。在那个评估点，基类是未定义的，导致NameError。
在try except语句中包装每个类都需要花费尽可能多的努力来重写模块，这样就可以解决这个问题了。
必须使用更高效的（在程序员时间方面）抑制NameError的方法。这可以通过使命名空间完全允许来实现，例如，如果查找对象不存在，则应该创建它，从而避免NameError。这种方法显然存在危险，因为查找会成为一种创造。
实现：
我相信Python中的命名空间是字典，字典方法可以重载，包括查找函数：__getitem__。所以mr_agreeable是一个带有重载__getitem__方法的字典子类，当查找键不存在时，它会自动创建一个空类。 mr_agreeable的一个实例作为classes.py脚本的命名空间传递给execfile。创建execfile调用的对象（除了内置函数之外）与调用脚本的globals（）dict合并：hack.py。
这是有效的，因为Python不关心类的基类是否在事后发生了变化。
这可能是依赖于实现的，我不知道。经测试：Win7 64bit上的Python 2.7.3 64位。
假设您的乱序类在classes.py中定义：
class ParentModel(object):
name = "parentmodel"
class ChildC(ChildA):
name = "childc"
class ChildA(ChildB):
name = "childa"
class ChildB(ParentModel):
name = "childb"
加载器脚本，我们称之为hack.py：
from random import randint
from codecs import encode
class mr_agreeable(dict):
sin_counter = 0
nutty_factor = 0
rdict = {0 : (0, 9), 200 : (10, 14), 500 : (15, 16), 550 : (17, 22)}
def __getitem__(self, key):
class tmp(object):
pass
tmp.__name__ = key
if(not key in self.keys()):
self.prognosis()
print self.insanity()
return self.setdefault(key, tmp)
def prognosis(self):
self.sin_counter += 1
self.nutty_factor = max(filter(lambda x: x < self.sin_counter, self.rdict.keys()))
def insanity(self):
insane_strs = \
[
"Nofbyhgryl", "Fher, jul abg?", "Sbe fher", "Fbhaqf terng", "Qrsvangryl", "Pbhyqa'g nterr zber",
"Jung pbhyq tb jebat?", "Bxl Qbnxl", "Lrc", "V srry gur fnzr jnl", "Zneel zl qnhtugre",
"Znlor lbh fubhyq svk gung", "1 AnzrReebe vf bar gbb znal naq n 1000'f abg rabhtu", "V'ir qbar qvegvre guvatf",
"Gur ebbz vf fgnegvat gb fcva", "Cebonoyl abg", "Npghnyyl, ab ..... nyevtug gura", "ZNXR VG FGBC",
"BU TBQ AB", "CYRNFR AB", "LBH'ER OERNXVAT CLGUBA", "GUVF VF ABG PBAFRAGHNY", "V'Z GRYYVAT THVQB!!"
]
return encode("ze_nterrnoyr: " + insane_strs[randint(*self.rdict[self.nutty_factor])], "rot13")
def the_act():
ns = mr_agreeable()
execfile("classes.py", ns)
hostages = list(set(ns.keys()) - set(["__builtins__", "object"]))
globals().update([(key, ns[key]) for key in hostages])
the_act()
mr_agreeable充当编译的classes.py的允许名称空间。他提醒你这是不好的形式。
答案 1 :(得分：0)
我之前的回答显示了一个加载器脚本，它在execfile中执行了乱序脚本，但提供了一个动态名称空间，用于创建占位符类（这些类通常是在定义之前获取的基类）。然后，它从加载器的全局命名空间中的此名称空间加载更改。
这种方法有两个问题：
1）它是一个黑客
2）占位符的假定类是对象类。所以当：
class ChildC(ChildA):
name = "childc"
被评估，命名空间检测到ChildA未定义，因此创建占位符类（对象子类）。当实际定义ChildA时（在无序脚本中），它可能与对象具有不同的基类，因此如果ChildA的基础不是对象类（ChildC最初创建的内容），则将ChildC重新绑定到新的ChildA将失败用）。有关详细信息，请参阅this。
所以我创建了一个新脚本，它实际上使用与之前的hack和this脚本类似的概念重写输入的乱序脚本。通过调用：
使用新脚本python mr_agreeable.py -i out_of_order.py -o ordered.py
mr_agreeable.py：
import os
import sys
from codecs import encode
from random import randint
import getopt
import inspect
import types
__doc__ = \
'''
A python script that re-orders out of sequence class defintions
'''
class rebase_meta(type):
'''
Rebase metaclass
Automatically rebases classes created with this metaclass upon
modification of classes base classes
'''
org_base_classes = {}
org_base_classes_subs = {}
base_classes = {}
base_classes_subs = {}
mod_loaded = False
mod_name = ""
mod_name_space = {}
def __init__(cls, cls_name, cls_bases, cls_dct):
#print "Making class: %s" % cls_name
super(rebase_meta, cls).__init__(cls_name, cls_bases, cls_dct)
# Remove the old base sub class listings
bases = rebase_meta.base_classes_subs.items()
for (base_cls_name, sub_dict) in bases:
sub_dict.pop(cls_name, None)
# Add class to bases' sub class listings
for cls_base in cls_bases:
if(not rebase_meta.base_classes_subs.has_key(cls_base.__name__)):
rebase_meta.base_classes_subs[cls_base.__name__] = {}
rebase_meta.base_classes[cls_base.__name__] = cls_base
rebase_meta.base_classes_subs[cls_base.__name__][cls_name] = cls
# Rebase the sub classes to the new base
if(rebase_meta.base_classes.has_key(cls_name)): # Is class a base class
subs = rebase_meta.base_classes_subs[cls_name]
rebase_meta.base_classes[cls_name] = cls # Update base class dictionary to new class
for (sub_cls_name, sub_cls) in subs.items():
if(cls_name == sub_cls_name):
continue
sub_bases_names = [x.__name__ for x in sub_cls.__bases__]
sub_bases = tuple([rebase_meta.base_classes[x] for x in sub_bases_names])
try:
# Attempt to rebase sub class
sub_cls.__bases__ = sub_bases
#print "Rebased class: %s" % sub_cls_name
except TypeError:
# The old sub class is incompatible with the new base class, so remake the sub
if(rebase_meta.mod_loaded):
new_sub_cls = rebase_meta(sub_cls_name, sub_bases, dict(sub_cls.__dict__.items() + [("__module__", rebase_meta.mod_name)]))
rebase_meta.mod_name_space[sub_cls_name] = new_sub_cls
else:
new_sub_cls = rebase_meta(sub_cls_name, sub_bases, dict(sub_cls.__dict__.items()))
subs[sub_cls_name] = new_sub_cls
@classmethod
def register_mod(self, imod_name, imod_name_space):
if(not self.mod_loaded):
self.org_base_classes = self.base_classes.copy()
self.org_base_classes_subs = self.base_classes_subs.copy()
self.mod_loaded = True
else:
self.base_classes = self.org_base_classes
self.base_classes_subs = self.org_base_classes_subs
self.mod_name = imod_name
self.mod_name_space = imod_name_space
# Can't subclass these classes
forbidden_subs = \
[
"bool",
"buffer",
"memoryview",
"slice",
"type",
"xrange",
]
# Builtin, sub-classable classes
org_class_types = filter(lambda x: isinstance(x, type) and (not x.__name__ in forbidden_subs) and x.__module__ == "__builtin__", types.__builtins__.values())
# Builtin classes recreated with Rebasing metaclass
class_types = [(cls.__name__, rebase_meta(cls.__name__, (cls,), {})) for cls in org_class_types]
# Overwrite builtin classes
globals().update(class_types)
class mr_quiet(dict):
'''
A namespace class that creates placeholder classes upon
a non existant lookup. mr_quiet doesnt say much.
'''
def __getitem__(self, key):
if(not key in self.keys()):
if(hasattr(__builtins__, key)):
return getattr(__builtins__, key)
else:
if(not key in self.keys()):
self.sanity_check()
return self.setdefault(key, rebase_meta(key, (object,), {}))
else:
return dict.__getitem__(self, key)
def sanity_check(self):
pass
class mr_agreeable(mr_quiet):
'''
A talkative cousin of mr_quiet.
'''
sin_counter = 0
nutty_factor = 0
rdict = {0 : (0, 9), 200 : (10, 14), 500 : (15, 16), 550 : (17, 22)}
def sanity_check(self):
self.prognogsis()
print self.insanity()
def prognogsis(self):
self.sin_counter += 1
self.nutty_factor = max(filter(lambda x: x < self.sin_counter, self.rdict.keys()))
def insanity(self):
insane_strs = \
[
"Nofbyhgryl", "Fher, jul abg?", "Sbe fher", "Fbhaqf terng", "Qrsvangryl", "Pbhyqa'g nterr zber",
"Jung pbhyq tb jebat?", "Bxl Qbnxl", "Lrc", "V srry gur fnzr jnl", "Zneel zl qnhtugre",
"Znlor lbh fubhyq svk gung", "1 AnzrReebe vf bar gbb znal naq n 1000'f abg rabhtu", "V'ir qbar qvegvre guvatf",
"Gur ebbz vf fgnegvat gb fcva", "Cebonoyl abg", "Npghnyyl, ab ..... nyevtug gura", "ZNXR VG FGBC",
"BU TBQ AB", "CYRNFR AB", "LBH'ER OERNXVAT CLGUBA", "GUVF VF ABG PBAFRAGHNY", "V'Z GRYYVAT THVQB!!"
]
return encode("ze_nterrnoyr: " + insane_strs[randint(*self.rdict[self.nutty_factor])], "rot13")
def coll_up(ilist, base = 0, count = 0):
'''
Recursively collapse nested lists at depth base and above
'''
tlist = []
if(isinstance(ilist, __builtins__.list) or isinstance(ilist, __builtins__.tuple)):
for q in ilist:
tlist += coll_up(q, base, count + 1)
else:
if(base > count):
tlist = ilist
else:
tlist = [ilist]
return [tlist] if((count != 0) and (base > count)) else tlist
def build_base_dict(ilist):
'''
Creates a dictionary of class : class bases pairs
'''
base_dict = {}
def build_base_dict_helper(iclass, idict):
idict[iclass] = list(iclass.__bases__)
for x in iclass.__bases__:
build_base_dict_helper(x, idict)
for cur_class in ilist:
build_base_dict_helper(cur_class, base_dict)
return base_dict
def transform_base_to_sub(idict):
'''
Transforms a base dict into dictionary of class : sub classes pairs
'''
sub_dict = {}
classes = idict.keys()
for cur_class in idict:
sub_dict[cur_class] = filter(lambda cls: cur_class in idict[cls], classes)
return sub_dict
recur_class_helper = lambda idict, ilist = []: [[key, recur_class_helper(idict, idict[key])] for key in ilist]
recur_class = lambda idict: recur_class_helper(idict, idict.keys())
class proc_func(list):
'''
Cmdline processing class
'''
def __init__(self, name = "", *args, **kwargs):
self.name = name
super(list, self).__init__(*args, **kwargs)
def get_args(self, *args):
self.extend(filter(lambda x: x, args))
def __call__(self, *args):
print self.name
print self
class proc_inputs(proc_func):
def get_args(self, *args):
self.extend(filter(os.path.isfile, args))
class proc_outputs(proc_func):
pass
class proc_helper(proc_func):
'''
Help function
Print help information
'''
def get_args(self, *args):
self()
def __call__(self, *args):
print __file__
print __doc__
print "Help:\n\t%s -h -i inputfile -o ouputfile" % sys.argv[0]
print "\t\t-h or --help\tPrint this help message"
print "\t\t-i or --input\tSpecifies the input script"
print "\t\t-o or --output\tSpecifies the output script"
sys.exit()
if __name__ == "__main__":
proc_input = proc_inputs("input")
proc_output = proc_outputs("output")
proc_help = proc_helper("help")
cmd_line_map = \
{
"-i" : proc_input,
"--input" : proc_input,
"-o" : proc_output,
"--ouput" : proc_output,
"-h" : proc_help,
"--help" : proc_help
}
try:
optlist, args = getopt.getopt(sys.argv[1:], "hi:o:", ["help", "input=", "output="])
for (key, value) in optlist:
cmd_line_map[key].get_args(value)
except getopt.GetoptError:
proc_help()
if(len(proc_input) != len(proc_output)):
print "Input files must have a matching output file"
proc_help()
elif(not proc_input):
proc_help()
else:
in_out_pairs = zip(proc_input, proc_output)
for (in_file, out_file) in in_out_pairs:
dodgy_module_name = os.path.splitext(in_file)[0]
sys.modules[dodgy_module_name] = types.ModuleType(dodgy_module_name)
sys.modules[dodgy_module_name].__file__ = in_file
# Make a fake space post haste
name_space = mr_agreeable\
(
[
("__name__", dodgy_module_name), # Needed for the created classes to identify with the fake module
("__module__", dodgy_module_name), # Needed to fool the inspect module
] + \
class_types
)
# Exclude these from returning
exclusions = name_space.keys()
# Associate the fake name space to the rebasing metaclass
rebase_meta.register_mod(dodgy_module_name, name_space)
# Run dodgy code
execfile(in_file, name_space)
# Bring back dodgy classes
import_classes = [cls if(isinstance(cls, type) and not cls_name in exclusions) else None for (cls_name, cls) in name_space.items()]
dodgy_import_classes = filter(lambda x: x, import_classes)
# Create base and sub class dictionaries
base_dict = build_base_dict(dodgy_import_classes)
sub_dict = transform_base_to_sub(base_dict)
# Create sets of base and sub classes
base_set = reduce(lambda x, y: x | y, map(set, base_dict.values()), set([]))
sub_set = reduce(lambda x, y: x | y, map(set, sub_dict.values()), set([]))
kings = list(base_set - sub_set) # A list of bases which are not subs
kingdoms = recur_class_helper(sub_dict, kings) # A subclass tree of lists
lineages = coll_up(kingdoms, 2) # Flatten the tree branches at and below 2nd level
# Filter only for the clases created in the dodgy module
inbred_lines = [filter(lambda x: x.__module__ == dodgy_module_name, lineage) for lineage in lineages]
# Load Source
for lineage in inbred_lines:
for cls in lineage:
setattr(cls, "_source", inspect.getsource(cls))
# Write Source
with open(out_file, "w") as file_h:
for lineage in inbred_lines:
for cls in lineage:
file_h.write(cls._source + "\n")