title: TypeError: cannot concatenate object of type '<class 'list'>'; only Series and DataFrame objs are valid
body: <p>I have a list of 10 dataframes named d0, d1, d2,...d9. All have 3 columns and 100 rows.</p>
  <pre><code>d0.info()
  &lt;class 'pandas.core.frame.DataFrame'&gt;
  RangeIndex: 100 entries, 0 to 99
  Data columns (total 3 columns):
   #   Column  Non-Null Count  Dtype  
  ---  ------  --------------  -----  
   0   0       100 non-null    float64
   1   1       100 non-null    float64
   2   2       100 non-null    float64
  dtypes: float64(3)
  memory usage: 2.5 KB
  </code></pre>
  <p>I want to merge all dataframes so that I can have 3 columns and 1000 rows and then convert it into an array.</p>
  <pre><code>s1=[d0,d1,d2,d3,d4,d5,d6,d7,d8,d9]
  s2=pd.concat([s1])
  </code></pre>
  <p>The above code throws error:</p>
  <pre><code>TypeError: cannot concatenate object of type '&lt;class 'list'&gt;'; only Series and DataFrame objs are valid
  
  type(s1)
  list
  </code></pre>
  <p>I used the solution suggested in <a href="https://stackoverflow.com/questions/61573099/pd-concat-in-pandas-is-giving-a-typeerror-cannot-concatenate-object-of-type-c?rq=1">pd.concat in pandas is giving a TypeError: cannot concatenate object of type &#39;&lt;class &#39;str&#39;&gt;&#39;; only Series and DataFrame objs are valid</a> ; however, got the above error.</p>