checking if column values are in a set pandas code example

Example 1: pandas check if value in column is in a list

df_new[df_new['l_ext'].isin([31, 22, 30, 25, 64])]

Example 2: pandas check if any of the values in one column exist in another

df["exists"] = df.drop("target", 1).isin(df["target"]).any(1)
print(df)

    target  A       B       C       exists
0   cat     bridge  cat     brush   True
1   brush   dog     cat     shoe    False
2   bridge  cat     shoe    bridge  True