<p>我有以下字符串:</p>
<pre><code>"It was in 1990. Then it was in 1992. Then it was in 2000. Then it was in 2005. Then it was in 2010."
</code></pre>
<p>我有以下regexp来匹配字符串中的年份:</p>
<pre><code>\d{4}
</code></pre>
<p>它与弦中存在的所有年份相匹配。我想要的是将regexp限制为只有第一个匹配,这样它就只能给出'1990'。我在pytho中使用以下代码:</p>
<pre><code>import re
s = "It was in 1990. Then it was in 1992. Then it was in 2000. Then it was in 2005. Then it was in 2010."
print re.findall(r"\d{4}", s)
['1990', '1992', '2000', '2005', '2010'] # output
</code></pre>
<p>我知道我可以通过添加[0]得到第一个,如下所示:</p>
<pre><code>print re.findall(r"\d{4}", s)[0]
1990 # output
</code></pre>
<p>但我特别寻找正则表达式模式来获得这个输出。你知道吗</p>