title: Python-docx: Changing line spacing for one table changes it in all tables
body: <p>I am relatively new to python-docx. I am trying to change the line spacing of a table in an existing document but it changes the line spacing of all the tables in the document.</p>
  <p>Here is a minimal, reproducible example, creating from scratch a document with three tables:</p>
  <pre class="lang-py prettyprint-override"><code>from docx import Document
  from docx.shared import Inches
  from docx.shared import Pt
  from docx.enum.text import WD_LINE_SPACING
  
  document = Document()
  
  # Some sample text to add to tables
  records = (
      (3, '101', 'Spam'),
      (7, '422', 'Eggs'),
      (4, '631', 'Spam, spam, eggs, and spam')
  )
  
  # Create table 0
  table = document.add_table(rows=1, cols=3)
  hdr_cells = table.rows[0].cells
  hdr_cells[0].text = 'Qty'
  hdr_cells[1].text = 'Id'
  hdr_cells[2].text = 'Desc'
  for qty, id, desc in records:
      row_cells = table.add_row().cells
      row_cells[0].text = str(qty)
      row_cells[1].text = id
      row_cells[2].text = desc
  
  document.add_page_break()
  
  # Create table 1
  table = document.add_table(rows=1, cols=3)
  hdr_cells = table.rows[0].cells
  hdr_cells[0].text = 'Qty'
  hdr_cells[1].text = 'Id'
  hdr_cells[2].text = 'Desc'
  for qty, id, desc in records:
      row_cells = table.add_row().cells
      row_cells[0].text = str(qty)
      row_cells[1].text = id
      row_cells[2].text = desc
  
  # Create table 2
  table = document.add_table(rows=1, cols=3)
  hdr_cells = table.rows[0].cells
  hdr_cells[0].text = 'Qty'
  hdr_cells[1].text = 'Id'
  hdr_cells[2].text = 'Desc'
  for qty, id, desc in records:
      row_cells = table.add_row().cells
      row_cells[0].text = str(qty)
      row_cells[1].text = id
      row_cells[2].text = desc
  
  # Print line spacing for all tables 
  for index, table in enumerate(document.tables):
      print(index, table.style.paragraph_format.line_spacing)
  </code></pre>
  <p>Output:</p>
  <pre><code>0 None
  1 None
  2 None
  </code></pre>
  <p>Then I try to change the line spacing only in the final table:</p>
  <pre class="lang-py prettyprint-override"><code>table = document.tables[2]
  table.style.paragraph_format.line_spacing_rule = WD_LINE_SPACING.EXACTLY
  table.style.paragraph_format.line_spacing = Pt(7)
  
  # Print line spacing for all tables
  for index, table in enumerate(document.tables):
      print(index, table.style.paragraph_format.line_spacing)
  </code></pre>
  <p>Output:</p>
  <pre><code>0 88900
  1 88900
  2 88900
  </code></pre>
  <p>You can see it has changed the line spacing for all of the tables - they are all now 7 pt (12 point is <code>152400</code>). If I try to change the reset the line spacing in the other tables, all the tables are updated with whatever the last value to be changed is.</p>
  <p>Here is my session info:</p>
  <pre><code>Session info --------------------------------------------------------------------
  Platform: Windows-7-6.1.7601-SP1 (64-bit)
  Python: 3.7
  Date: 2020-09-21
  Packages ------------------------------------------------------------------------
  python-docx==0.8.10
  reprexpy==0.3.0
  </code></pre>
  <p>Is this a bug or am I doing something wrong?</p>