how to output duplicate ids from dataframe python code example

Example 1: find duplicated rows with respect to multiple columns pandas

df = df[df.duplicated(subset=['val1','val2'], keep=False)]
print (df)
   id  val1  val2
0   1   1.1   2.2
1   1   1.1   2.2
3   3   8.8   6.2
4   4   1.1   2.2
5   5   8.8   6.2

Example 2: python - show repeted values in a column

df = df[df.duplicated(subset=['val1','val2'], keep=False)]