Pandas: Split a string and then create a new column?

Question

Let's say you have Col1.

How do you create the new column 'Col2' after you split the string values in Col1 until you see _?

Answer 1

Edit to handle strings without '_':

df['Col2'] = (np.where(df['Col1'].str.contains('_'),
                  df['Col1'].str.split('_').str[1],
                  df['Col1']))

OR as COLDSPEED suggests in comments:

df['Col1'].str.split('_').str[-1]

You can use the .str access with indexing:

df['Col2'] = df['Col1'].str.split('_').str[1]

Example:

df = pd.DataFrame({'Col1':['Name_John','Name_Jay','Name_Sherry']})
df['Col2'] = df['Col1'].str.split('_').str[1]

Output:

          Col1    Col2
0    Name_John    John
1     Name_Jay     Jay
2  Name_Sherry  Sherry