blocks|key|123044|text|由于前导0，013是一个八进制整数文字(相当于十进制整数文字11)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|123045|>>>+2013*013
22143
>>>+2013*11
22143
>>>+2013*13
26169|code-block|syntax|javascript|123046|八进制整数文字以0开头，十六进制整数文字以0x开头是非常常见的(当然在我熟悉的大多数语言中都是如此)。由于您所经历的完全混乱，Python3引发了一个SyntaxError：|123047|>>>+2013*013
++File+"<stdin>",+line+1
++++2013*013
+++++++++++%5E
SyntaxError:+invalid+token|123048|并且需要使用0o或0O：|123049|>>>+2013*0o13
22143
>>>+2013*0O13
22143+|123050|entityMap^0|6|3|U|2|0|0|8|1|L|2|0|0|6|2|9|2|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@$9|17|A|18|B|C]|$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|T|$]]

<code>013</code> is an octal integer literal (equivalent to the decimal integer literal <code>11</code>), due to the leading 0.

<pre><code>&gt;&gt;&gt; 2013*013
22143
&gt;&gt;&gt; 2013*11
22143
&gt;&gt;&gt; 2013*13
26169
</code></pre>

It is very common (certainly in most of the languages I'm familiar with) to have octal integer literals start with <code>0</code> and hexadecimal integer literals start with <code>0x</code>. Due to the exact confusion you experienced, Python 3 raises a SyntaxError:

<pre><code>&gt;&gt;&gt; 2013*013
 File "&lt;stdin&gt;", line 1
 2013*013
 ^
SyntaxError: invalid token
</code></pre>

and requires either <code>0o</code> or <code>0O</code> instead:

<pre><code>&gt;&gt;&gt; 2013*0o13
22143
&gt;&gt;&gt; 2013*0O13
22143 
</code></pre>

blocks|key|340896|text|这在很大程度上只是对@Wim的回答进行了一点扩展，但Python使用某些前缀来表示整数字面量的基础。如果没有前缀，整数将被解释为以10为基数。对于"0x"，整数将被解释为十六进制整数。完整的语法规范在这里，尽管如果您不熟悉形式语法就有点难以理解：http://docs.python.org/2/reference/lexical_analysis.html#integers|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|340897|这张表基本上是说，如果你想要一个长值(即一个超过普通int的容量的值)，请写数字，后跟字母"L“或"l"；如果你想用十进制解释数字，请正常写数字(没有前导0)；如果你想用八进制解释，请在它前面加上"0”、"0o“或"0O"；如果你想用十六进制，请在它前面加上"0x"；如果你想用二进制，请在它前面加上"0B”或"0b“。|340898|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/2/reference/lexical_analysis.html#integers^0|3F|1T|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

This is mostly just expanding on @Wim's answer a bit, but Python indicates the base of integer literals using certain prefixes. Without a prefix, integers are interpreted as being in base-10. With an "0x", the integer will be interpreted as a hexadecimal int. The full grammar specification is here, though it's a bit tricky to understand if you're not familiar with formal grammars: <a href="http://docs.python.org/2/reference/lexical_analysis.html#integers" rel="nofollow">http://docs.python.org/2/reference/lexical_analysis.html#integers</a>

The table essentially says that if you want a long value (i.e. one that exceeds the capacity of a normal int), write the number followed by the letter "L" or "l"; if you want your number to be interpreted in decimal, write the number normally (with no leading 0); if you want it interpreted in octal, prefix it with "0", "0o", or "0O"; if you want it in hex, prefix it with "0x"; and if you want it in binary, prefix it with "0b" or "0B".

blocks|key|123173|text|Python用于八进制文字的“前导零”语法是一个常见的陷阱：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|123174|Python+2.7.3
>>>+010
8|code-block|syntax|javascript|123175|Python+3.x+http://docs.python.org/3.0/whatsnew/3.0.html#integers中的语法已更改|offset|length|123176|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.python.org/3.0/whatsnew/3.0.html#integers^0|0|0|B|1H|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]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Python's 'leading zero' syntax for octal literals is a common gotcha:

<pre><code>Python 2.7.3
&gt;&gt;&gt; 010
8
</code></pre>

The syntax was changed in Python 3.x <a href="http://docs.python.org/3.0/whatsnew/3.0.html#integers" rel="nofollow">http://docs.python.org/3.0/whatsnew/3.0.html#integers</a>

Just starting out with Python, so this is probably my mistake, but...

I'm trying out Python. I like to use it as a calculator, and I'm slowly working through some tutorials.

I ran into something weird today. I wanted to find out 2013*2013, but I wrote the wrong thing and wrote 2013*013, and got this:

<pre><code>&gt;&gt;&gt; 2013*013
22143
</code></pre>

I checked with my calculator, and 22143 is the wrong answer! 2013 * 13 is supposed to be 26169.

Why is Python giving me a wrong answer? My old Casio calculator doesn't do this...

Wrong math with Python?

刚开始使用Python，所以这可能是我的错误，但是...我正在试用Python。我喜欢把它当做计算器使用，我正在慢慢地学习一些教程。我今天遇到了一些奇怪的事情。我想找出2013*2013，但我写错了东西，写成了2013*013，结果是这样的：>>> 2013*01322143我用我的计算器检查了一下，22143是错误的...

问Python的数学错误？
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