title: How to split and rename columns at the same instance in pandas?
body: <p>I have a dataframe called <code>thyroid_df</code>.</p>
  <pre><code>&gt;&gt;&gt; thyroid_df
                        0  1         2
  0    chr1:233276815:A:G  A  0.277632
  1    chr2:217427435:C:G  C  0.357674
  2    chr3:169800667:T:G  T  0.207014
  3      chr5:1279675:C:T  T  0.182322
  4    chr5:112150207:A:T  A  0.314811
  5     chr8:32575278:G:T  G  0.277632
  6     chr9:97775520:A:C  A  0.524729
  7   chr10:103934543:C:T  T  0.343590
  8    chr14:36063370:G:C  G  0.329304
  9    chr14:36269155:C:T  T  0.593327
  10   chr15:67165147:G:C  C  0.207014
  11   chr15:67163292:C:T  T  0.215111
  </code></pre>
  <p>I want to split the first column by <code>:</code> and rename the column names. I tried this below which doesn't seem to work. I want to rename column names with the same line of code.</p>
  <p><code>thyroid_df[0].str.split(':', 3, expand=True).rename(columns = [&quot;CHROM&quot;, &quot;POS_GRCh38&quot;, &quot;REF&quot;, &quot;Effect_allele&quot;])</code></p>