title: What does "ValueError: No objects to concatenate" mean and how can I fix it?
body: <p>I try to get data from google trends in a g sheet. First time it runned smoothly, second time not so much. I got an error called:</p>
  <blockquote>
  <p>ValueError: No objects to concatenate</p>
  </blockquote>
  <p>I searched this error on Stack Overflow before but couldn't find any solutions. I use the code displayed below:</p>
  <pre><code>!pip install Pytrends
  !pip install pandas
  !pip install pytrends --upgrade &lt;---------Note: this solved a different error.
  from pytrends.request import TrendReq
  import pandas as pd
  import time
  startTime = time.time()
  pytrend = TrendReq(hl='nl-NL', tz=360)
  df = wb = gc.open_by_url('https://docs.google.com/spreadsheets/d/1QE1QilM-GDdQle6eVunepqG5RNWv39xO0By84C19Ehc/edit?usp=sharing')
  sheet = wb.sheet1
  df2 = sheet.col_values(5)
  d_from = sheet.acell('B7').value
  d_to = sheet.acell('B8').value
  geo1 = sheet.acell('B10').value
  dataset = []
  for x in range(1,len(df2)):
       keywords = [df2[x]]
       pytrend.build_payload(
       kw_list=keywords,
       cat=0,
       timeframe= str(d_from + &quot; &quot; + d_to),
       geo= str(geo1))
       data = pytrend.interest_over_time()
       if not data.empty:
            data = data.drop(labels=['isPartial'],axis='columns')
            dataset.append(data)
  result = pd.concat(dataset, axis=1)
  result.to_csv('search_trends_DOWNLOAD_ME.csv')
  !cp search_trends_DOWNLOAD_ME.csv &quot;/content/drive/My Drive/Colab Notebooks/Output&quot;
  executionTime = (time.time() - startTime)
  print('Execution time in sec.: ' + str(executionTime))
  </code></pre>
  <p>The error I got:</p>
  <pre class="lang-none prettyprint-override"><code>ValueError                                Traceback (most recent call last)
  &lt;ipython-input-5-b86c7b4df727&gt; in &lt;module&gt;()
       25           data = data.drop(labels=['isPartial'],axis='columns')
       26           dataset.append(data)
  ---&gt; 27 result = pd.concat(dataset, axis=1)
       28 result.to_csv('search_trends_DOWNLOAD_ME.csv')
       29 get_ipython().system('cp search_trends_DOWNLOAD_ME.csv &quot;/content/drive/My Drive/Colab Notebooks/Output&quot;')
  
  1 frames
  /usr/local/lib/python3.6/dist-packages/pandas/core/reshape/concat.py in __init__(self, objs, axis, join, keys, levels, names, ignore_index, verify_integrity, copy, sort)
      327 
      328         if len(objs) == 0:
  --&gt; 329             raise ValueError(&quot;No objects to concatenate&quot;)
      330 
      331         if keys is None:
  
  ValueError: No objects to concatenate
  </code></pre>
  <p>The keywords I use are located in <code>df = wb = gc.open_by_url</code>. It is a g-sheet with the location, language and the keywords.</p>