title: What do empty braces mean in Python?
body: <p>Please have a look at this snippet:</p>
  
  <pre><code>import xlrd,spss
  from xlrd import open_workbook
  wb=open_workbook('C:/temp/testbook.xls')
  sheetnames=[]
  for s in wb.sheets():
     sheetnames.append(s.name)
  </code></pre>
  
  <p>Why should I write "<code>wb.sheets()</code>" instead of "<code>wb.sheets</code>"? And why is it "<code>s.name</code>" instead of "<code>s.name()</code>"? </p>
  
  <p>I often use empty braces when I'm not supposed to and the other way around. Could anybody tell me what they mean and when I should (not) use them?</p>