blocks|key|1126304|text|if+type(x)+is+list:
++++print+'a+list'
elif+type(x)+is+tuple:
++++print+'a+tuple'
else:
++++print+'neither+a+tuple+or+a+list'|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1126305|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>if type(x) is list:
 print 'a list'
elif type(x) is tuple:
 print 'a tuple'
else:
 print 'neither a tuple or a list'
</code></pre>

blocks|key|1341291|text|只要不是多余的，使用isinstance就没有错。如果一个变量应该只是一个列表/元组，那么记录该接口，并按此方式使用它。否则，检查是完全合理的：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1341292|if+isinstance(a,+collections.Iterable):
++++#+use+as+a+container
else:
++++#+not+a+container!|code-block|syntax|javascript|1341293|这种类型的检查确实有一些很好的用例，比如使用标准字符串startswith+/+endswith方法(尽管准确地说，这些方法是用CPython中的C实现的，使用显式检查来查看它是否是一个元组-有不止一种方法可以解决这个问题，正如您所链接的文章中提到的那样)。|1341294|显式检查通常比尝试使用对象作为容器并处理异常更好-这可能会导致代码部分运行或不必要地运行时出现各种问题。|1341295|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/library/stdtypes.html#str.startswith|1|http://docs.python.org/library/stdtypes.html#str.endswith^0|A|A|0|0|R|A|0|14|8|1|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@]|D|@$9|13|A|14|1|15]|$9|16|A|17|1|18]]|E|$]]|$1|M|3|N|5|6|7|19|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|1A|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]|W|$5|R|S|T|E|$U|X]]]]

There's nothing wrong with using <code>isinstance</code> as long as it's not redundant. If a variable should only be a list/tuple then document the interface and just use it as such. Otherwise a check is perfectly reasonable:

<pre><code>if isinstance(a, collections.Iterable):
 # use as a container
else:
 # not a container!
</code></pre>

This type of check does have some good use-cases, such as with the standard string <a href="http://docs.python.org/library/stdtypes.html#str.startswith" rel="noreferrer">startswith</a> / <a href="http://docs.python.org/library/stdtypes.html#str.endswith" rel="noreferrer">endswith</a> methods (although to be accurate these are implemented in C in CPython using an explicit check to see if it's a tuple - there's more than one way to solve this problem, as mentioned in the article you link to).

An explicit check is often better than trying to use the object as a container and handling the exception - that can cause all sorts of problems with code being run partially or unnecessarily.

blocks|key|1126035|text|将参数记录为需要是序列的参数，并将其用作序列。不要检查类型。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126036|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Document the argument as needing to be a sequence, and use it as a sequence. Don't check the type.

blocks|key|1341471|text|hasattr(a,+"__iter__")怎么样？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1341472|它告诉我们返回的对象是否可以作为生成器进行迭代。默认情况下，元组和列表可以，但字符串类型不能。|1341473|entityMap^0|0|M|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

How about: <code>hasattr(a, "__iter__")</code> ?

It tells if the object returned can be iterated over as a generator. By default, tuples and lists can, but not the string types.

blocks|key|1341517|text|在Python2.8上，type(list)+is+list返回false|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1341518|我建议用这种可怕的方式来比较类型：|1341519|if+type(a)+==+type([])+:
++print+"variable+a+is+a+list"|code-block|syntax|javascript|1341520|(至少在我的系统上，在Mac+OS+X+Yosemite上使用anaconda+)|1341521|entityMap^0|C|I|W|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|X|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

On Python 2.8 <code>type(list) is list</code> returns <code>false</code> 
I would suggest comparing the type in this horrible way:

<pre><code>if type(a) == type([]) :
 print "variable a is a list"
</code></pre>

(well at least on my system, using anaconda on Mac OS X Yosemite)

blocks|key|1341425|text|>>>+l+=+[]
>>>+l.__class__.__name__+in+('list',+'tuple')
True|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1341426|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>&gt;&gt;&gt; l = []
&gt;&gt;&gt; l.__class__.__name__ in ('list', 'tuple')
True
</code></pre>

blocks|key|1341391|text|Python使用“鸭子类型”，即如果一个变量像鸭子一样叫醒，那么它一定是一只鸭子。在您的例子中，您可能希望它是可迭代的，或者您希望访问某个索引处的项。你应该这样做:例如，在try块中使用for+var:或var[idx]中的对象，如果你得到一个异常，它不是一个鸭子……|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1341392|entityMap^0|2E|3|2L|8|2U|8|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

Python uses "Duck typing", i.e. if a variable kwaks like a duck, it must be a duck. In your case, you probably want it to be iterable, or you want to access the item at a certain index. You should just do this: i.e. use the object in <code>for var:</code> or <code>var[idx]</code> inside a <code>try</code> block, and if you get an exception it wasn't a duck...

blocks|key|1126494|text|确定变量是列表还是元组或一般检查变量类型的另一种简单方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126495|++++def+islist(obj):

++++++++if+("list"+in+str(type(obj))+):+return+True

++++++++else+:+return+False|code-block|syntax|javascript|1126496|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|$]]

Another easy way to find out if a variable is either list or tuple or generally check variable type would be :

<pre><code> def islist(obj):

 if ("list" in str(type(obj)) ): return True

 else : return False
</code></pre>

blocks|key|1341416|text|如果只需要知道是否可以对变量使用foo[123]表示法，可以使用hasattr(foo,+'__getitem__')检查是否存在__getitem__属性(这是按索引访问时python调用的属性|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1341417|entityMap^0|G|8|W|R|1T|B|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|O|8|@]|D|@]|E|$]]]|G|$]]

If you just need to know if you can use the <code>foo[123]</code> notation with the variable, you can check for the existence of a <code>__getitem__</code> attribute (which is what python calls when you access by index) with <code>hasattr(foo, '__getitem__')</code>

blocks|key|1341574|text|如果你真的想要像函数参数一样处理任何东西，就必须进行更复杂的测试。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1341575|type(a)+!=+type('')+and+hasattr(a,+"__iter__")|code-block|syntax|javascript|1341576|不过，通常只要明确指出一个函数需要iterable，然后只检查type(a)+!=+type('')就足够了。|offset|length|style|CODE|1341577|此外，对于一个字符串，你可能有一个简单的处理路径，或者你想要友好地做一个拆分等等，所以你不想对字符串大喊大叫，如果有人给你发了一些奇怪的东西，就让他有一个异常。|1341578|entityMap^0|0|0|V|J|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Has to be more complex test if you really want to handle just about anything as function argument.

<pre><code>type(a) != type('') and hasattr(a, "__iter__")
</code></pre>

Although, usually it's enough to just spell out that a function expects iterable and then check only <code>type(a) != type('')</code>. 

Also it may happen that for a string you have a simple processing path or you are going to be nice and do a split etc., so you don't want to yell at strings and if someone sends you something weird, just let him have an exception.

blocks|key|1126518|text|不是最优雅的，但我做到了(对于Python+3)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1126519|if+hasattr(instance,+'__iter__')+and+not+isinstance(instance,+(str,+bytes)):
++++...|code-block|syntax|javascript|1126520|这允许其他可迭代(如Django查询集)，但不包括字符串和字节串。我通常在接受单个对象ID或对象ID列表的函数中使用它。有时对象ID可以是字符串，我不想逐个字符地迭代这些字符。:)|1126521|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Not the most elegant, but I do (for Python 3):
<pre><code>if hasattr(instance, '__iter__') and not isinstance(instance, (str, bytes)):
 ...
</code></pre>
This allows other iterables (like Django querysets) but excludes strings and bytestrings. I typically use this in functions that accept either a single object ID or a list of object IDs. Sometimes the object IDs can be strings and I don't want to iterate over those character by character. :)

blocks|key|1341659|text|你知道..。我这样做可能很愚蠢，但我是这样做的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1341660|try:
++++len(thing)
except:
++++#+not+a+list|code-block|syntax|javascript|1341661|就像，如果我能知道它的长度，它肯定不止一件。|1341662|编辑:我刚刚意识到，如果非列表项是一个字符串(因为字符串本质上是一个字符列表)，它将不起作用。|1341663|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You know... I may be doing this the stupid way, but I do this:
<pre><code>try:
 len(thing)
except:
 # not a list
</code></pre>
Like, if I can know the length of it, it gotta be more than one thing.
Edit: Just realized it won't work if the non-list item is a string (since a string is essentially a list of characters).

In python, what's the best way to test if a variable contains a list or a tuple? (ie. a collection)

Is <code>isinstance()</code> as evil as suggested here? <a href="http://www.canonical.org/~kragen/isinstance/" rel="noreferrer">http://www.canonical.org/~kragen/isinstance/</a>

Update: the most common reason I want to distinguish a list from a string is when I have some indefinitely deep nested tree / data-structure of lists of lists of lists of strings etc. which I'm exploring with a recursive algorithm and I need to know when I've hit the "leaf" nodes.

Test if a variable is a list or tuple

在python中，测试变量是否包含列表或元组的最佳方法是什么？(即一个集合)：isinstance()真的像这里所说的那么邪恶吗？更新:我想要区分列表和字符串的最常见原因是，当我有一些无限深的嵌套树/字符串列表的数据结构时，我正在使用递归算法进行探索，并且我需要知道我何时命中了“叶子”节点。

问测试变量是列表还是元组
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