blocks|key|755398|text|在Python中，您可以执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|755399|test+=+float("inf")|code-block|syntax|javascript|755400|在Python+3.5中，您可以执行以下操作：|755401|import+math
test+=+math.inf|755402|然后：|755403|test+>+1
test+>+10000
test+>+x|755404|将永远是正确的。当然，除非如所指出的那样，x也是无穷大或"nan“(”不是数字“)。|755405|此外(仅限Python2.x)，与Ellipsis相比，float(inf)更小，例如：|offset|length|style|CODE|755406|float('inf')+<+Ellipsis|755407|将返回true。|755408|entityMap^0|0|0|0|0|0|0|0|H|8|S|A|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|14|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|16|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|19|8|@$S|1A|T|1B|U|V]|$S|1C|T|1D|U|V]]|9|@]|A|$]]|$1|W|3|X|5|D|7|1E|8|@]|9|@]|A|$E|F]]|$1|Y|3|Z|5|6|7|1F|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|11|$]]

In Python, you can do:

<pre><code>test = float("inf")
</code></pre>

In Python 3.5, you can do:

<pre><code>import math
test = math.inf
</code></pre>

And then:

<pre><code>test &gt; 1
test &gt; 10000
test &gt; x
</code></pre>

Will always be true. Unless of course, as pointed out, x is also infinity or "nan" ("not a number").

Additionally (Python 2.x ONLY), in a comparison to <code>Ellipsis</code>, <code>float(inf)</code> is lesser, e.g:

<pre><code>float('inf') &lt; Ellipsis
</code></pre>

would return true.

blocks|key|538896|text|从Python3.5开始，您可以使用math.inf|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|538897|>>>+import+math
>>>+math.inf
inf|code-block|syntax|javascript|538898|entityMap^0|I|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Since Python 3.5 you can use <code>math.inf</code>:

<pre><code>&gt;&gt;&gt; import math
&gt;&gt;&gt; math.inf
inf
</code></pre>

blocks|key|755602|text|似乎没有人明确提到负无穷大，所以我想我应该加上它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|755603|对于负无穷大：|755604|-math.inf|code-block|syntax|javascript|755605|对于正无穷大(只是为了完整性)：|755606|math.inf|755607|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|$]]

No one seems to have mentioned about the negative infinity explicitly, so I think I should add it.
For negative infinity:
<pre><code>-math.inf
</code></pre>
For positive infinity (just for the sake of completeness):
<pre><code>math.inf
</code></pre>

blocks|key|755344|text|我不知道你到底在做什么，但是float("inf")给了你一个浮点无穷大，它比任何其他数字都大。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|755345|entityMap^0|E|C|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

I don't know exactly what you are doing, but <code>float("inf")</code> gives you a float Infinity, which is greater than any other number.

blocks|key|538940|text|在NumPy库中有一个无穷大的值：from+numpy+import+inf。要获得负无穷大，可以简单地编写-inf。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|538941|entityMap^0|H|L|1I|4|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

There is an infinity in the NumPy library: <code>from numpy import inf</code>. To get negative infinity one can simply write <code>-inf</code>.

blocks|key|755432|text|另一种不太方便的方法是使用Decimal类：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|755433|from+decimal+import+Decimal
pos_inf+=+Decimal('Infinity')
neg_inf+=+Decimal('-Infinity')|code-block|syntax|javascript|755434|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/2/library/decimal.html^0|D|7|D|7|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

Another, less convenient, way to do it is to use <a href="http://docs.python.org/2/library/decimal.html" rel="noreferrer"><code>Decimal</code></a> class:

<pre><code>from decimal import Decimal
pos_inf = Decimal('Infinity')
neg_inf = Decimal('-Infinity')
</code></pre>

blocks|key|755480|text|在python2.x中有一个用于此目的的肮脏的黑客攻击(除非绝对必要，否则永远不要使用它)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|755481|None+<+any+integer+<+any+string|code-block|syntax|javascript|755482|因此，校验i+<+''保存任意整数i的True。|offset|length|style|CODE|755483|它在python3中已经被合理地弃用了。现在，这样的比较结果是|755484|TypeError:+unorderable+types:+str()+<+int()|755485|entityMap^0|0|0|5|6|H|1|J|4|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@$I|V|J|W|K|L]|$I|X|J|Y|K|L]|$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|R|$]]

In python2.x there was a dirty hack that served this purpose (NEVER use it unless absolutely necessary):

<pre><code>None &lt; any integer &lt; any string
</code></pre>

Thus the check <code>i &lt; ''</code> holds <code>True</code> for any integer <code>i</code>.

It has been reasonably deprecated in python3. Now such comparisons end up with

<pre><code>TypeError: unorderable types: str() &lt; int()
</code></pre>

blocks|key|539214|text|另外，如果你使用SymPy，你也可以使用sympy.oo|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|539215|>>>+from+sympy+import+oo
>>>+oo+%2B+1
oo
>>>+oo+-+oo
nan|code-block|syntax|javascript|539216|等。|539217|entityMap^0|K|8|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Also if you use SymPy you can use <code>sympy.oo</code>

<pre><code>&gt;&gt;&gt; from sympy import oo
&gt;&gt;&gt; oo + 1
oo
&gt;&gt;&gt; oo - oo
nan
</code></pre>

etc.

blocks|key|755855|text|对于正无穷|type|unstyled|depth|inlineStyleRanges|entityRanges|data|755856|pos_inf_val+=+float("infinity")|code-block|syntax|javascript|755857|对于负无穷大|755858|neg_inf_val+=+float("-infinity")|755859|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]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

For Positive Infinity
<pre><code>pos_inf_val = float(&quot;infinity&quot;)
</code></pre>
For Negative Infinity
<pre><code>neg_inf_val = float(&quot;-infinity&quot;)
</code></pre>

How can I represent an infinite number in python? No matter which number you enter in the program, no number should be greater than this representation of infinity.

How can I represent an infinite number in Python?

如何在python中表示无穷大的数字？无论您在程序中输入哪个数字，任何数字都不应大于这个无穷大的表示。

问如何在Python中表示无穷大的数字？
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