title: If values from two columns in two different data frames match then copy values from another column in df2 to column in df1
body: <p>I have two data frames, and I want to copy values from the column "Result2" in df2 to column "Result1" in df1 and to add the column "Description" from df2 to df1 for values that are in the same row as values from the column "Result2" (that are already copied), if the values from columns "ID" in both data frames match.</p>
  
  <p>Here are the data frames:</p>
  
  <p>df1</p>
  
  <pre><code>ID              Result1
  Position1       NaN
  MRS1            OK
  MRS2            Maybe
  MRS3            NOK
  Position2       NaN
  MRS4            OK
  MRS5            OK
  Position3       NaN
  MRS6            OK
  Position4       NaN
  MRS7            NOK
  MRS8            OK
  MRS9            NOK
  MRS10           Excellent
  </code></pre>
  
  <p>df2</p>
  
  <pre><code>ID              Result2              Description
  text            NaN                  NaN
  NaN             NaN                  text
  text            NaN                  NaN
  MRS1            OK                   New
  MRS2            OK                   Old
  NaN             NaN                  NaN
  NaN             NaN                  text
  MRS3            OK                   New
  MRS4            OK                   New
  MRS5            OK                   NaN
  MRS6            NOK                  Very old
  NaN             text                 NaN
  text            text                 NaN
  NaN             NaN                  NaN
  MRS7            Excellent            Very old
  MRS8            Excellent            Old
  text            text                 text
  MRS9            Excellent            New
  NaN             NaN                  NaN
  MRS10           NOK                  New
  </code></pre>
  
  <p>I want to get:</p>
  
  <pre><code>ID              Result1             Result2
  Position1       NaN                  NaN
  MRS1            OK                   New
  MRS2            OK                   Old
  MRS3            OK                   New
  Position2       NaN                  NaN
  MRS4            OK                   New
  MRS5            OK                   NaN            
  Position3       NaN                  NaN
  MRS6            NOK                  Very old
  Position4       NaN                  NaN
  MRS7            Excellent            Very old
  MRS8            Excellent            Old
  MRS9            Excellent            New
  MRS10           NOK                  New
  </code></pre>
  
  <p>and I put NaN on the places where should be an empty cell. How to do this in pandas?
  I tried with the merge, but I have the problem because it is required the same length of comparing columns. I just want to compare values from the "ID" columns from both data frames, and those columns do not have the same length.</p>