title: Pandas: query string where column name contains special characters
body: <p>I am working with a data frame that has a structure something like the following:</p>
  
  <pre><code>In[75]: df.head(2)
  Out[75]: 
    statusdata             participant_id association  latency response  \
  0   complete  CLIENT-TEST-1476362617727       seeya      715  dislike   
  1   complete  CLIENT-TEST-1476362617727      welome      800     like   
  
     stimuli elementdata statusmetadata demo$gender  demo$question2  \
  0  Sample B    semi_imp       complete        male              23   
  1  Sample C    semi_imp       complete      female              23   
  </code></pre>
  
  <p>I want to be able to run a query string against the column <code>demo$gender</code>.</p>
  
  <p>I.e,</p>
  
  <pre><code>df.query("demo$gender=='male'")
  </code></pre>
  
  <p>But this has a problem with the <code>$</code> sign. If I replace the <code>$</code> sign with another delimited (like <code>-</code>) then the problem persists. Can I fix up my query string to avoid this problem. I would prefer not to rename the columns as these correspond tightly with other parts of my application.</p>
  
  <p>I really want to stick with a query string as it is supplied by another component of our tech stack and creating a parser would be a heavy lift for what seems like a simple problem.</p>
  
  <p>Thanks in advance.</p>