title: "ValueError: Columns must be same length as key" when filtering dataframe with isin(list)
body: <p>I am trying to filter a column in my dataframe based on values from a list, here is the snippet of my code where it's going wrong (replaced values for simplicity's sake)</p>
  <pre><code>import pandas as pd
  from pandas import Series
  
  df['Campaign']=df['Location']
  campaign_list = ['a', 'b']
  df['Campaign']=df[df['Campaign'].isin(campaign_list)]
  
  </code></pre>
  <p>here is an example of what the dataframe looks like before the problem code</p>
  <pre><code>Location    Billed Amount   TransactionID   Campaign
  a           Na              x               a
  b           Na              y               b
  c           Na              z               c
  d           Na              xx              d
  e           Na              xy              e
  f           Na              xz              f
  </code></pre>
  <p>here is what my desired df should look like</p>
  <pre><code>Location    Billed Amount   TransactionID   Campaign
  a           NaN             x               a
  b           NaN             y               b
  c           NaN             z               NaN
  d           NaN             xx              NaN
  e           NaN             xy              NaN
  f           NaN             xz              NaN
  </code></pre>
  <p>Here is the error I am receiving, which is strange because I ran this exact code yesterday and didn't have any issue. Is there something obvious here I'm just not seeing?</p>
  <pre><code>~\anaconda3\lib\site-packages\pandas\core\frame.py in __setitem__(self, key, value)
     3600             self._setitem_array(key, value)
     3601         elif isinstance(value, DataFrame):
  -&gt; 3602             self._set_item_frame_value(key, value)
     3603         elif (
     3604             is_list_like(value)
  
  ~\anaconda3\lib\site-packages\pandas\core\frame.py in _set_item_frame_value(self, key, value)
     3727             len_cols = 1 if is_scalar(cols) else len(cols)
     3728             if len_cols != len(value.columns):
  -&gt; 3729                 raise ValueError(&quot;Columns must be same length as key&quot;)
     3730 
     3731             # align right-hand-side columns if self.columns
  
  ValueError: Columns must be same length as key
  </code></pre>