title: What's the difference between df.head() and df.head?
body: <p>In Jupyter Notebook or terminal, both df.head and df.head() can return an output of the dataframe, with some minor differences. What's the fundamental difference between the two different expressions and what role does parenthesis play in Python in general?
  Thanks!</p>
  
  <pre><code>&gt;&gt;&gt;df.head
  &lt;bound method NDFrame.head of          Date    Open    High     Low   Close    Volume
  0    1-Jun-17  153.17  153.33  152.22  153.18  16404088
  1    2-Jun-17  153.58  155.45  152.89  155.45  27770715
  2    5-Jun-17  154.34  154.45  153.46  153.93  25331662
  3    6-Jun-17  153.90  155.81  153.78  154.45  26624926
  4    7-Jun-17  155.02  155.98  154.48  155.37  21069647
  5    8-Jun-17  155.25  155.54  154.40  154.99  21250798
  6    9-Jun-17  155.19  155.19  146.02  148.98  64882657
  7   12-Jun-17  145.74  146.09  142.51  145.42  72307330
  8   13-Jun-17  147.16  147.45  145.15  146.59  34165445
  9   14-Jun-17  147.50  147.50  143.84  145.16  31531232
  10  15-Jun-17  143.32  144.48  142.21  144.29  32165373
  &gt;&gt;&gt; df.head()
         Date    Open    High     Low   Close    Volume
  0  1-Jun-17  153.17  153.33  152.22  153.18  16404088
  1  2-Jun-17  153.58  155.45  152.89  155.45  27770715
  2  5-Jun-17  154.34  154.45  153.46  153.93  25331662
  3  6-Jun-17  153.90  155.81  153.78  154.45  26624926
  4  7-Jun-17  155.02  155.98  154.48  155.37  21069647
  </code></pre>