title: How can I check what data type of variables of dataframe in one time?
body: <p>I have a dataframe object 'df' which have a lot of columns(variables). These variables have different data type, for example:</p>
  
  <pre><code>&gt;&gt;&gt; df.thal.head()
  0    6.0
  1    3.0
  2    7.0
  3    3.0
  4    3.0
  Name: thal, dtype: object
  </code></pre>
  
  <p>Obviously, 'thal' variable data type is object. I can use</p>
  
  <pre><code>df.thal.astype(float)
  </code></pre>
  
  <p>to change its data type. But i have a great many variables and i can't check them one by one.</p>
  
  <p>Is there some ways check all of variables data type and then change their data type in one time?</p>
  
  <p>Thanks.</p>