blocks|key|168939|text|一般而言：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|168940|foo[somestuff]|code-block|syntax|javascript|168941|调用__getitem__或__setitem__。(还有__getslice__和__setslice__，但它们现在已被弃用，因此我们不再讨论它们)。现在，如果somestuff中有一个逗号，python将向底层函数传递一个tuple：|offset|length|style|CODE|168942|foo[1,2]++#+passes+a+tuple|168943|如果有:，python将传递一个分片：|168944|foo[:]++#+passes+`slice(None,+None,+None)`
foo[1:2]++#+passes+`slice(1,+2,+None)`
foo[1:2:3]++#+passes+`slice(1,+2,+3)
foo[1::3]++#+passes+`slice(1,+None,+3)|168945|希望你能明白这一点。现在，如果有一个逗号和一个冒号，python将传递一个包含切片的元组。在您的示例中：|168946|foo[:,+1]++#+passes+the+tuple+`(slice(None,+None,+None),+1)`|168947|对象(foo)对输入做什么完全取决于对象。|168948|entityMap^0|0|0|2|B|E|B|T|C|16|C|2A|9|36|5|0|0|3|1|0|0|0|0|3|3|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@$I|13|J|14|K|L]|$I|15|J|16|K|L]|$I|17|J|18|K|L]|$I|19|J|1A|K|L]|$I|1B|J|1C|K|L]|$I|1D|J|1E|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|1F|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1G|8|@$I|1H|J|1I|K|L]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|1J|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1K|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|1L|8|@]|9|@]|A|$E|F]]|$1|W|3|X|5|6|7|1M|8|@$I|1N|J|1O|K|L]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1P|8|@]|9|@]|A|$]]]|Z|$]]

Generally speaking:

<pre><code>foo[somestuff]
</code></pre>

calls either <code>__getitem__</code>, or <code>__setitem__</code>. (there's also <code>__getslice__</code> and <code>__setslice__</code>, but those are now deprecated, so let's not talk about that). Now, if <code>somestuff</code> has a comma in it, python will pass a <code>tuple</code> to the underlying function:

<pre><code>foo[1,2] # passes a tuple
</code></pre>

If there is a <code>:</code>, python will pass a slice:

<pre><code>foo[:] # passes `slice(None, None, None)`
foo[1:2] # passes `slice(1, 2, None)`
foo[1:2:3] # passes `slice(1, 2, 3)
foo[1::3] # passes `slice(1, None, 3)
</code></pre>

Hopefully you get the idea. Now if there is a comma and a colon, python will pass a tuple which contains a slice. in your example:

<pre><code>foo[:, 1] # passes the tuple `(slice(None, None, None), 1)`
</code></pre>

What the object (<code>foo</code>) does with the input is entirely up to the object.

blocks|key|4674818|text|假设list是一个2D+(numpy)数组，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4674819|[[+1,+2,+3],
+[+4,+5,+6],
+[+7,+8,+9]]|code-block|syntax|javascript|4674820|list[1,1]++#+-->+5|4674821|它显示选择position+1,1中的元素|4674822|list[:,1]++#+-->+[2,5,8]+
list[1][1]++#+-->+5
list[:][1]++#+-->+[4+5+6]|4674823|有关更多示例，请参阅this和this。|4674824|entityMap|0|LINK|mutability|MUTABLE|url|note+that+indexes+start+from+zero|1|http://scipy-lectures.org/intro/numpy/array_object.html|2|https://numpy.org/doc/stable/reference/arrays.indexing.html^0|2|4|0|0|0|E|3|0|0|0|A|4|1|F|4|2|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|H|7|18|8|@]|D|@]|E|$I|J]]|$1|M|3|N|5|6|7|19|8|@]|D|@$9|1A|A|1B|1|1C]]|E|$]]|$1|O|3|P|5|H|7|1D|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|1E|8|@]|D|@$9|1F|A|1G|1|1H]|$9|1I|A|1J|1|1K]]|E|$]]|$1|S|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]|10|$5|V|W|X|E|$Y|11]]|12|$5|V|W|X|E|$Y|13]]]]

Lets assume <code>list</code> is a 2D (numpy) array as follows:
<pre><code>[[ 1, 2, 3],
 [ 4, 5, 6],
 [ 7, 8, 9]]
</code></pre>
<pre><code>list[1,1] # --&gt; 5
</code></pre>
It says select the element in position [1,1] (note that indexes start from zero)
<pre><code>list[:,1] # --&gt; [2,5,8] 
list[1][1] # --&gt; 5
list[:][1] # --&gt; [4 5 6]
</code></pre>
See <a href="http://scipy-lectures.org/intro/numpy/array_object.html" rel="nofollow noreferrer">this</a> and <a href="https://numpy.org/doc/stable/reference/arrays.indexing.html" rel="nofollow noreferrer">this</a> for further examples.

blocks|key|4674877|text|在某种意义上，逗号分隔您尝试从中选择的数组的不同维度。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4674878|假设我有一个二维数组|4674879|my_array+=+numpy.array([[1,2,3],
++++++++++++++++++++++++[4,5,6],
++++++++++++++++++++++++[7,8,9]])|code-block|syntax|javascript|4674880|通过这样做，我可以选择行(0和1)和列(1和2)：|4674881|#+++++++++++++rows+%7C+cols
print(my_array[0:2,+1:3])+#+prints+[[2+3]
++++++++++++++++++++++++++++++++++++[5+6]]|4674882|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

In a sense the comma separates the different dimensions of your array that you are trying to select from.
Lets say I have a 2D array
<pre><code>my_array = numpy.array([[1,2,3],
 [4,5,6],
 [7,8,9]])
</code></pre>
I could select rows(0 and 1) and columns(1 and 2) by doing this:
<pre><code># rows | cols
print(my_array[0:2, 1:3]) # prints [[2 3]
 [5 6]]
</code></pre>

I met this in a python script <code>list[:, 1]</code> and I am trying to figure out the role of the comma.

What does a colon and comma stand in a python list?

我在python脚本list[:, 1]中遇到了这一点，我正在尝试弄清楚逗号的作用。

问python列表中的冒号和逗号代表什么？
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问python列表中的冒号和逗号代表什么？
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