title: Select row based on date and change value in other column python pandas
body: <p>In my dataframe (~200k rows), i convert value in column "Date" to week number, based on ISO-standard week:</p>
  
  <pre><code>import pandas as pd
  
  df["Week Number"] = df["Date"].dt.week 
  </code></pre>
  
  <p>And my df look like this:</p>
  
  <pre><code>Date   | Column1 | Week Number
  ------+---------+--------
  1/1/16  | A       | 1
  2/1/16  | B       | 1
  3/1/16  | C       | 1
  8/1/16  | A       | 2
  9/1/16  | B       | 2
  10/1/16 | C       | 2
  15/1/17 | A       | 2
  16/1/17 | B       | 2
  17/1/17 | C       | 2
  </code></pre>
  
  <p>But i want add +52 in row "Week Number", if this row is from 2017 in column "Date":</p>
  
  <pre><code>Date   | Column1 | Week Number
  ------+---------+--------
  1/1/16  | A       | 1
  2/1/16  | B       | 1
  3/1/16  | C       | 1
  8/1/16  | A       | 2
  9/1/16  | B       | 2
  10/1/16 | C       | 2
  15/1/17 | A       | 54
  16/1/17 | B       | 54
  17/1/17 | C       | 54
  </code></pre>
  
  <p>How make solution in pandas/numpy or something lib in python3?</p>