blocks|key|956042|text|print+my_string[0:100]|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|956043|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>print my_string[0:100]
</code></pre>

blocks|key|956052|text|简单：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|956053|print+mystring[:100]|code-block|syntax|javascript|956054|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|$]]

Easy:

<pre><code>print mystring[:100]
</code></pre>

blocks|key|956176|text|为了回答Philipp的担忧(在评论中)，切片也可以用于unicode字符串|type|unstyled|depth|inlineStyleRanges|entityRanges|data|956177|>>>+greek=u"αβγδεζηθικλμνξοπρςστυφχψω"
>>>+print+len(greek)
25
>>>+print+greek[:10]
αβγδεζηθικ|code-block|syntax|javascript|956178|如果您希望将上述代码作为脚本运行，请将此行放在顶部|956179|#+-*-+coding:+utf-8+-*-|956180|如果您的编辑器未保存为utf-8格式，请替换为正确的编码|956181|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

To answer Philipp's concern ( in the comments ), slicing works ok for unicode strings too

<pre><code>&gt;&gt;&gt; greek=u"αβγδεζηθικλμνξοπρςστυφχψω"
&gt;&gt;&gt; print len(greek)
25
&gt;&gt;&gt; print greek[:10]
αβγδεζηθικ
</code></pre>

If you want to run the above code as a script, put this line at the top

<pre><code># -*- coding: utf-8 -*-
</code></pre>

If your editor doesn't save in utf-8, substitute the correct encoding

blocks|key|1170378|text|数组的切片是使用[first:last%2B1]完成的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1170379|我经常使用的一个技巧是用省略号表示额外的信息。因此，如果您的字段是100个字符，我将使用：|1170380|if+len(s)+<=+100:
++++print+s
else:
++++print+"%25s..."%25(s[:97])|code-block|syntax|javascript|1170381|是的，我知道在这种情况下，对于%25格式化操作符，()是多余的，这正是我的风格。|1170382|entityMap^0|8|E|0|0|0|F|1|N|2|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|V|8|@$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

Slicing of arrays is done with <code>[first:last+1]</code>.

One trick I tend to use a lot of is to indicate extra information with ellipses. So, if your field is one hundred characters, I would use:

<pre><code>if len(s) &lt;= 100:
 print s
else:
 print "%s..."%(s[:97])
</code></pre>

And yes, I know <code>()</code> is superfluous in this case for the <code>%</code> formatting operator, it's just my style.

blocks|key|1170510|text|使用%25设置字符串格式是处理此问题的一种很好的方法。这里有一些例子。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1170511|格式化代码'%25s'将'12345'转换为字符串，但它已经是一个字符串。|1170512|>>>+'%25s'+%25+'12345'

'12345'|code-block|syntax|javascript|1170513|'%25.3s'指定仅使用前三个字符。|1170514|>>>+'%25.3s'+%25+'12345'

'123'|1170515|'%25.7s'说要使用前七个字符，但只有五个。没问题。|1170516|>>>+'%25.7s'+%25+'12345'

'12345'|1170517|'%257s'最多使用七个字符，用左边的空格填充缺少的字符。|1170518|>>>+'%257s'+%25+'12345'

'++12345'|1170519|除了在右边填充缺少的字符之外，'%25-7s'也是一样的。|1170520|>>>+'%25-7s'+%25+'12345'

'12345++'|1170521|'%255.3'说使用前三个字符，但在左边填充空格，总共五个字符。|1170522|>>>+'%255.3s'+%25+'12345'

'++123'|1170523|同样的事情除了填在右边。|1170524|>>>+'%25-5.3s'+%25+'12345'

'123++'|1170525|也可以处理多个参数！|1170526|>>>+'do+u+no+%25-4.3sda%253.2s+wae'+%25+('12345',+6789)

'do+u+no+123+da+67+wae'|1170527|如果您需要更高的灵活性，也可以使用str.format()。两个都是Here+is+documentation。|1170528|entityMap|0|LINK|mutability|MUTABLE|url|https://pyformat.info/^0|2|1|0|5|4|A|7|0|0|0|6|0|0|0|6|0|0|0|5|0|0|F|6|0|0|0|6|0|0|0|0|0|0|H|C|Y|L|0|0^^$0|@$1|2|3|4|5|6|7|1O|8|@$9|1P|A|1Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1R|8|@$9|1S|A|1T|B|C]|$9|1U|A|1V|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|1W|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1X|8|@$9|1Y|A|1Z|B|C]]|D|@]|E|$]]|$1|O|3|P|5|J|7|20|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|21|8|@$9|22|A|23|B|C]]|D|@]|E|$]]|$1|S|3|T|5|J|7|24|8|@]|D|@]|E|$K|L]]|$1|U|3|V|5|6|7|25|8|@$9|26|A|27|B|C]]|D|@]|E|$]]|$1|W|3|X|5|J|7|28|8|@]|D|@]|E|$K|L]]|$1|Y|3|Z|5|6|7|29|8|@$9|2A|A|2B|B|C]]|D|@]|E|$]]|$1|10|3|11|5|J|7|2C|8|@]|D|@]|E|$K|L]]|$1|12|3|13|5|6|7|2D|8|@$9|2E|A|2F|B|C]]|D|@]|E|$]]|$1|14|3|15|5|J|7|2G|8|@]|D|@]|E|$K|L]]|$1|16|3|17|5|6|7|2H|8|@]|D|@]|E|$]]|$1|18|3|19|5|J|7|2I|8|@]|D|@]|E|$K|L]]|$1|1A|3|1B|5|6|7|2J|8|@]|D|@]|E|$]]|$1|1C|3|1D|5|J|7|2K|8|@]|D|@]|E|$K|L]]|$1|1E|3|1F|5|6|7|2L|8|@$9|2M|A|2N|B|C]]|D|@$9|2O|A|2P|1|2Q]]|E|$]]|$1|1G|3|-4|5|6|7|2R|8|@]|D|@]|E|$]]]|1H|$1I|$5|1J|1K|1L|E|$1M|1N]]]]

String formatting using <code>%</code> is a great way to handle this. Here are some examples.

The formatting code <code>'%s'</code> converts <code>'12345'</code> to a string, but it's already a string.

<pre><code>&gt;&gt;&gt; '%s' % '12345'

'12345'
</code></pre>

<code>'%.3s'</code> specifies to use only the first three characters.

<pre><code>&gt;&gt;&gt; '%.3s' % '12345'

'123'
</code></pre>

<code>'%.7s'</code> says to use the first seven characters, but there are only five. No problem.

<pre><code>&gt;&gt;&gt; '%.7s' % '12345'

'12345'
</code></pre>

<code>'%7s'</code> uses up to seven characters, filling missing characters with spaces on the left.

<pre><code>&gt;&gt;&gt; '%7s' % '12345'

' 12345'
</code></pre>

<code>'%-7s'</code> is the same thing, except filling missing characters on the right.

<pre><code>&gt;&gt;&gt; '%-7s' % '12345'

'12345 '
</code></pre>

<code>'%5.3'</code> says use the first three characters, but fill it with spaces on the left to total five characters.

<pre><code>&gt;&gt;&gt; '%5.3s' % '12345'

' 123'
</code></pre>

Same thing except filling on the right.

<pre><code>&gt;&gt;&gt; '%-5.3s' % '12345'

'123 '
</code></pre>

Can handle multiple arguments too!

<pre><code>&gt;&gt;&gt; 'do u no %-4.3sda%3.2s wae' % ('12345', 6789)

'do u no 123 da 67 wae'
</code></pre>

If you require even more flexibility, <code>str.format()</code> is available too. <a href="https://pyformat.info/" rel="nofollow noreferrer">Here is documentation</a> for both.

blocks|key|1170468|text|前面的大多数示例都会在字符串不够长的情况下引发异常。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1170469|另一种方法是使用'yourstring'.ljust(100)[:100].strip()。|offset|length|style|CODE|1170470|这将为您提供前100个字符。如果你的字符串最后一个字符是空格，你可能会得到一个更短的字符串。|1170471|entityMap^0|0|8|11|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

Most of previous examples will raise an exception in case your string is not long enough.

Another approach is to use 
<code>'yourstring'.ljust(100)[:100].strip()</code>.

This will give you first 100 chars.
You might get a shorter string in case your string last chars are spaces.

blocks|key|956379|text|[start:stop:step]|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|956380|因此，如果你只想获取100个第一个字符，使用your_string[0:100]或your_string[:100]如果你想只获取偶数位置的字符，那么使用your_string[::2]。对于start是0，对于字符串的stop+-+len是0，对于step+-+1。所以当你没有提供其中之一并放入':‘时，它将使用默认值。|unstyled|offset|length|style|CODE|956381|entityMap^0|0|M|I|15|H|25|G|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]|$G|Q|H|R|I|J]|$G|S|H|T|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|U|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>[start:stop:step]
</code></pre>

So If you want to take only 100 first character, use <code>your_string[0:100]</code> or <code>your_string[:100]</code>
If you want to take only the character at even position, use <code>your_string[::2]</code>
The "default values" for start is 0, for stop - len of string, and for step - 1. So when you don't provide one of its and put ':', it'll use it default value.

Can seem to find a substring function in python.

Say I want to output the first 100 characters in a string, how can I do this? 

I want to do it safely also, meaing if the string is 50 characters it shouldn't fail.

Output first 100 characters in a string

似乎可以在python中找到一个子串函数。假设我想输出字符串中的前100个字符，我该怎么做呢？我也想安全地这样做，意思是如果字符串是50个字符，它应该不会失败。

问输出字符串中的前100个字符
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