如何使用pyYAML將python元組添加到YAML文件中？

Question

標題不言自明。

當我一個元組保存到YAML文件，我得到的東西看起來是這樣的：

ambient: !!python/tuple [0.3, 0.3 ,0.3] 

當我試着使用yaml.safe_load（FILE_OBJECT）來加載它，我不斷收到讀取錯誤：

yaml.constructor.ConstructorError: could not determine a constructor for the tag 'tag:yaml.org,2002:python/tuple' 

需要做什麼？

Answer 1

在pyyaml中，SafeLoader不包含python本機類​​型的加載器，僅包含yaml規範中定義的類型。您可以在下面的交互示例中看到SafeLoader和Loader的類型。

您可以定義一個新的Loader類在Python元組增加了，而不是其他類型的，所以應該還是很安全：導致

import yaml 

class PrettySafeLoader(yaml.SafeLoader): 
    def construct_python_tuple(self, node): 
     return tuple(self.construct_sequence(node)) 

PrettySafeLoader.add_constructor(
    u'tag:yaml.org,2002:python/tuple', 
    PrettySafeLoader.construct_python_tuple) 

doc = yaml.dump(tuple("foo bar baaz".split())) 
print repr(doc) 
thing = yaml.load(doc, Loader=PrettySafeLoader) 
print thing 

：

'!!python/tuple [foo, bar, baaz]\n' 
('foo', 'bar', 'baaz') 

見下文用於與SafeLoader和Loader類關聯的構造函數。

>>> yaml.SafeLoader.yaml_constructors 
{None: <unbound method SafeConstructor.construct_undefined>, 
u'tag:yaml.org,2002:binary': <unbound method SafeConstructor.construct_yaml_binary>, 
u'tag:yaml.org,2002:bool': <unbound method SafeConstructor.construct_yaml_bool>, 
u'tag:yaml.org,2002:float': <unbound method SafeConstructor.construct_yaml_float>, 
u'tag:yaml.org,2002:int': <unbound method SafeConstructor.construct_yaml_int>, 
u'tag:yaml.org,2002:map': <unbound method SafeConstructor.construct_yaml_map>, 
u'tag:yaml.org,2002:null': <unbound method SafeConstructor.construct_yaml_null>, 
u'tag:yaml.org,2002:omap': <unbound method SafeConstructor.construct_yaml_omap>, 
u'tag:yaml.org,2002:pairs': <unbound method SafeConstructor.construct_yaml_pairs>, 
u'tag:yaml.org,2002:seq': <unbound method SafeConstructor.construct_yaml_seq>, 
u'tag:yaml.org,2002:set': <unbound method SafeConstructor.construct_yaml_set>, 
u'tag:yaml.org,2002:str': <unbound method SafeConstructor.construct_yaml_str>, 
u'tag:yaml.org,2002:timestamp': <unbound method SafeConstructor.construct_yaml_timestamp>} 

>>> yaml.Loader.yaml_constructors 
{None: <unbound method SafeConstructor.construct_undefined>, 
u'tag:yaml.org,2002:binary': <unbound method SafeConstructor.construct_yaml_binary>, 
u'tag:yaml.org,2002:bool': <unbound method SafeConstructor.construct_yaml_bool>, 
u'tag:yaml.org,2002:float': <unbound method SafeConstructor.construct_yaml_float>, 
u'tag:yaml.org,2002:int': <unbound method SafeConstructor.construct_yaml_int>, 
u'tag:yaml.org,2002:map': <unbound method SafeConstructor.construct_yaml_map>, 
u'tag:yaml.org,2002:null': <unbound method SafeConstructor.construct_yaml_null>, 
u'tag:yaml.org,2002:omap': <unbound method SafeConstructor.construct_yaml_omap>, 
u'tag:yaml.org,2002:pairs': <unbound method SafeConstructor.construct_yaml_pairs>, 
u'tag:yaml.org,2002:python/bool': <unbound method Constructor.construct_yaml_bool>, 
u'tag:yaml.org,2002:python/complex': <unbound method Constructor.construct_python_complex>, 
u'tag:yaml.org,2002:python/dict': <unbound method Constructor.construct_yaml_map>, 
u'tag:yaml.org,2002:python/float': <unbound method Constructor.construct_yaml_float>, 
u'tag:yaml.org,2002:python/int': <unbound method Constructor.construct_yaml_int>, 
u'tag:yaml.org,2002:python/list': <unbound method Constructor.construct_yaml_seq>, 
u'tag:yaml.org,2002:python/long': <unbound method Constructor.construct_python_long>, 
u'tag:yaml.org,2002:python/none': <unbound method Constructor.construct_yaml_null>, 
u'tag:yaml.org,2002:python/str': <unbound method Constructor.construct_python_str>, 
u'tag:yaml.org,2002:python/tuple': <unbound method Constructor.construct_python_tuple>, 
u'tag:yaml.org,2002:python/unicode': <unbound method Constructor.construct_python_unicode>, 
u'tag:yaml.org,2002:seq': <unbound method SafeConstructor.construct_yaml_seq>, 
u'tag:yaml.org,2002:set': <unbound method SafeConstructor.construct_yaml_set>, 
u'tag:yaml.org,2002:str': <unbound method SafeConstructor.construct_yaml_str>, 
u'tag:yaml.org,2002:timestamp': <unbound method SafeConstructor.construct_yaml_timestamp>} 

Answer 2

至少根據the PyYAML documentation：

功能yaml.safe_load限制這種能力像整數或列表簡單Python對象。

列表as you can see in the source比較廣泛，但不包括tag:yaml.org,2002:python/tuple。

看來，如果您在YAML文件中生成!!python/tuple類型，那麼您使用的是dump()而不是safe_dump()。如果是這種情況，您應該切換到使用load()代替safe_load()，因爲由dump()創建的文件不能保證可由safe_load()加載。 （見description of safe_dump()）。