blocks|key|1495756|text|这可能是可行的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1495757|import+sys

def+str_to_class(classname):
++++return+getattr(sys.modules[__name__],+classname)|code-block|syntax|javascript|1495758|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This could work:

<pre><code>import sys

def str_to_class(classname):
 return getattr(sys.modules[__name__], classname)
</code></pre>

blocks|key|1495736|text|你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1495737|globals()[class_name]|code-block|syntax|javascript|1495738|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You could do something like:

<pre><code>globals()[class_name]
</code></pre>

blocks|key|1281141|text|您需要类Baz，它位于模块foo.bar中。在Python2.7中，您希望使用importlib.import_module()，因为这将使向Python3的转换更容易：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1281142|import+importlib

def+class_for_name(module_name,+class_name):
++++#+load+the+module,+will+raise+ImportError+if+module+cannot+be+loaded
++++m+=+importlib.import_module(module_name)
++++#+get+the+class,+will+raise+AttributeError+if+class+cannot+be+found
++++c+=+getattr(m,+class_name)
++++return+c|code-block|syntax|javascript|1281143|使用Python+<+2.7：|1281144|def+class_for_name(module_name,+class_name):
++++#+load+the+module,+will+raise+ImportError+if+module+cannot+be+loaded
++++m+=+__import__(module_name,+globals(),+locals(),+class_name)
++++#+get+the+class,+will+raise+AttributeError+if+class+cannot+be+found
++++c+=+getattr(m,+class_name)
++++return+c|1281145|使用：|1281146|loaded_class+=+class_for_name('foo.bar',+'Baz')|1281147|entityMap^0|4|3|D|7|13|P|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|14|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|16|8|@]|D|@]|E|$]]]|T|$]]

You want the class <code>Baz</code>, which lives in module <code>foo.bar</code>. With Python 2.7,
you want to use <code>importlib.import_module()</code>, as this will make transitioning to Python 3 easier: 

<pre><code>import importlib

def class_for_name(module_name, class_name):
 # load the module, will raise ImportError if module cannot be loaded
 m = importlib.import_module(module_name)
 # get the class, will raise AttributeError if class cannot be found
 c = getattr(m, class_name)
 return c
</code></pre>

With Python &lt; 2.7:

<pre><code>def class_for_name(module_name, class_name):
 # load the module, will raise ImportError if module cannot be loaded
 m = __import__(module_name, globals(), locals(), class_name)
 # get the class, will raise AttributeError if class cannot be found
 c = getattr(m, class_name)
 return c
</code></pre>

Use:

<pre><code>loaded_class = class_for_name('foo.bar', 'Baz')
</code></pre>

blocks|key|1496012|text|我已经了解了django是如何处理这个问题的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1496013|django.utils.module_loading有这样的功能|offset|length|1496014|def+import_string(dotted_path):
++++"""
++++Import+a+dotted+module+path+and+return+the+attribute/class+designated+by+the
++++last+name+in+the+path.+Raise+ImportError+if+the+import+failed.
++++"""
++++try:
++++++++module_path,+class_name+=+dotted_path.rsplit('.',+1)
++++except+ValueError:
++++++++msg+=+"%25s+doesn't+look+like+a+module+path"+%25+dotted_path
++++++++six.reraise(ImportError,+ImportError(msg),+sys.exc_info()[2])

++++module+=+import_module(module_path)

++++try:
++++++++return+getattr(module,+class_name)
++++except+AttributeError:
++++++++msg+=+'Module+"%25s"+does+not+define+a+"%25s"+attribute/class'+%25+(
++++++++++++module_path,+class_name)
++++++++six.reraise(ImportError,+ImportError(msg),+sys.exc_info()[2])|code-block|syntax|javascript|1496015|您可以像使用import_string("module_path.to.all.the.way.to.your_class")一样使用它|style|CODE|1496016|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/django/django/blob/main/django/utils/module_loading.py^0|0|0|R|0|0|0|6|1L|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@$D|Y|E|Z|1|10]]|A|$]]|$1|F|3|G|5|H|7|11|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|12|8|@$D|13|E|14|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

I've looked at how django handles this
<a href="https://github.com/django/django/blob/main/django/utils/module_loading.py" rel="nofollow noreferrer">django.utils.module_loading</a> has this
<pre><code>def import_string(dotted_path):
 &quot;&quot;&quot;
 Import a dotted module path and return the attribute/class designated by the
 last name in the path. Raise ImportError if the import failed.
 &quot;&quot;&quot;
 try:
 module_path, class_name = dotted_path.rsplit('.', 1)
 except ValueError:
 msg = &quot;%s doesn't look like a module path&quot; % dotted_path
 six.reraise(ImportError, ImportError(msg), sys.exc_info()[2])

 module = import_module(module_path)

 try:
 return getattr(module, class_name)
 except AttributeError:
 msg = 'Module &quot;%s&quot; does not define a &quot;%s&quot; attribute/class' % (
 module_path, class_name)
 six.reraise(ImportError, ImportError(msg), sys.exc_info()[2])
</code></pre>
You can use it like <code>import_string(&quot;module_path.to.all.the.way.to.your_class&quot;)</code>

blocks|key|1495811|text|import+sys
import+types

def+str_to_class(field):
++++try:
++++++++identifier+=+getattr(sys.modules[__name__],+field)
++++except+AttributeError:
++++++++raise+NameError("%25s+doesn't+exist."+%25+field)
++++if+isinstance(identifier,+(types.ClassType,+types.TypeType)):
++++++++return+identifier
++++raise+TypeError("%25s+is+not+a+class."+%25+field)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1495812|这可以准确地处理旧式和新式类。|unstyled|1495813|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>import sys
import types

def str_to_class(field):
 try:
 identifier = getattr(sys.modules[__name__], field)
 except AttributeError:
 raise NameError("%s doesn't exist." % field)
 if isinstance(identifier, (types.ClassType, types.TypeType)):
 return identifier
 raise TypeError("%s is not a class." % field)
</code></pre>

This accurately handles both old-style and new-style classes.

blocks|key|1281036|text|是的，你可以做到。假设您的类存在于全局名称空间中，则如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1281037|import+types

class+Foo:
++++pass

def+str_to_class(s):
++++if+s+in+globals()+and+isinstance(globals()[s],+types.ClassType):
++++++++++++return+globals()[s]
++++return+None

str_to_class('Foo')

==>+<class+__main__.Foo+at+0x340808cc>|code-block|syntax|javascript|1281038|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Yes, you can do this. Assuming your classes exist in the global namespace, something like this will do it:

<pre><code>import types

class Foo:
 pass

def str_to_class(s):
 if s in globals() and isinstance(globals()[s], types.ClassType):
 return globals()[s]
 return None

str_to_class('Foo')

==&gt; &lt;class __main__.Foo at 0x340808cc&gt;
</code></pre>

blocks|key|1281198|text|对于任意代码执行或不需要的用户传递的名称，您可以有一个可接受的函数/类名的列表，如果输入与列表中的一个匹配，则对其求值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1281199|PS:+I+know....kinda+late....but这是给将来遇到这个问题的任何人的。|1281200|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

In terms of arbitrary code execution, or undesired user passed names, you could have a list of acceptable function/class names, and if the input matches one in the list, it is eval'd.

PS: I know....kinda late....but it's for anyone else who stumbles across this in the future.

blocks|key|1496045|text|我不明白这为什么行不通。它不像其他人的答案那样具体，但是如果你知道你的类名，那么它就足够了。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1496046|def+str_to_class(name):
++++if+name+==+"Foo":
++++++++return+Foo
++++elif+name+==+"Bar":
++++++++return+Bar|code-block|syntax|javascript|1496047|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I don't see why this wouldn't work. It's not as concrete as everyone else's answers but if you know the name of your class then it's enough.
<pre class="lang-python prettyprint-override"><code>def str_to_class(name):
 if name == &quot;Foo&quot;:
 return Foo
 elif name == &quot;Bar&quot;:
 return Bar
</code></pre>

Given a string as user input to a Python function, I'd like to get a class object out of it if there's a class with that name in the currently defined namespace. Essentially, I want the implementation for a function which will produce this kind of result:

<pre><code>class Foo:
 pass

str_to_class("Foo")
==&gt; &lt;class __main__.Foo at 0x69ba0&gt;
</code></pre>

Is this, at all, possible?

Convert string to Python class object?

Python

给定一个字符串作为Python函数的用户输入，如果在当前定义的名称空间中存在具有该名称的类，我希望从中获取一个类对象。本质上，我想要一个函数的实现，它将产生这样的结果：class Foo: passstr_to_class("Foo")==> <class __main__.Foo at 0x69ba0>这到底有没有可能？

问是否将字符串转换为Python类对象？
EN

回答 8

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