title: MemoryError: Unable to allocate array with shape and data type object
body: <p>I want to perform an inner join between two dataset which looks like:</p>
  <pre><code>theme_ids.head()
  id  Loan Theme ID   Loan Theme Type Partner ID
  0   638631  a1050000000skGl General 151
  1   640322  a1050000000skGl General 151
  2   641006  a1050000002X1ij Higher Education    160
  3   641019  a1050000002X1ij Higher Education    160
  4   641594  a1050000002VbsW Subsistence Agriculture 336
  </code></pre>
  <p>and</p>
  <pre><code>theme_reg.head()
  Partner ID  Field Partner Name  sector  Loan Theme ID   Loan Theme Type country forkiva region  geocode_old ISO ... amount  LocationName    geocode names   geo lat lon mpi_region  mpi_geo rural_pct
  0   9   KREDIT Microfinance Institution General Financial Inclusion a1050000000slfi Higher Education    Cambodia    No  Banteay Meanchey    (13.75, 103.0)  KHM ... 450 Banteay Meanchey, Cambodia  [(13.6672596, 102.8975098)] Banteay Meanchey Province; Cambodia (13.6672596, 102.8975098)   13.667259   102.897507  Banteay Mean Chey, Cambodia (13.6672596, 102.8975098)   90
  1   9   KREDIT Microfinance Institution General Financial Inclusion a10500000068jPe Vulnerable Populations  Cambodia    No  Battambang Province NaN KHM ... 20275   Battambang Province, Cambodia   [(13.0286971, 102.989615)]  Battambang Province; Cambodia   (13.0286971, 102.989615)    13.028697   102.989616  Banteay Mean Chey, Cambodia (13.6672596, 102.8975098)   90
  2   9   KREDIT Microfinance Institution General Financial Inclusion a1050000000slfi Higher Education    Cambodia    No  Battambang Province NaN KHM ... 9150    Battambang Province, Cambodia   [(13.0286971, 102.989615)]  Battambang Province; Cambodia   (13.0286971, 102.989615)    13.028697   102.989616  Banteay Mean Chey, Cambodia (13.6672596, 102.8975098)   90
  3   9   KREDIT Microfinance Institution General Financial Inclusion a10500000068jPe Vulnerable Populations  Cambodia    No  Kampong Cham Province   (12.0, 105.5)   KHM ... 604950  Kampong Cham Province, Cambodia [(12.0982918, 105.3131185)] Kampong Cham Province; Cambodia (12.0982918, 105.3131185)   12.098291   105.313118  Kampong Cham, Cambodia  (11.9924294, 105.4645408)   90
  4   9   KREDIT Microfinance Institution General Financial Inclusion a1050000002X1Uu Sanitation  Cambodia    No  Kampong Cham Province   (12.0, 105.5)   KHM ... 275 Kampong Cham Province, Cambodia [(12.0982918, 105.3131185)] Kampong Cham Province; Cambodia (12.0982918, 105.3131185)   12.098291   105.313118  Kampong Cham, Cambodia  (11.9924294, 105.4645408)   90
  </code></pre>
  <p>I've tried:</p>
  <pre><code>data = pd.merge(theme_ids, theme_reg, on='Partner ID', how='inner') 
  </code></pre>
  <p>which raises:</p>
  <blockquote>
  <p>MemoryError: Unable to allocate array with shape (15, 144356281) and
  data type object</p>
  </blockquote>