python select dataframe values code example

Example 1: selecting a specific value and corrersponding value in df python

#To select rows whose column value equals a scalar, some_value, use ==:df.loc[df['favorite_color'] == 'yellow']

Example 2: add an index column in range dataframe

df = df.loc[df.index.repeat(df['a'])]   
df['c'] = df.groupby(level=0).cumcount() + 1
df = df.reset_index(drop=True)
print (df)
   a  b  c
0  1  x  1
1  2  y  1
2  2  y  2
3  3  z  1
4  3  z  2
5  3  z  3