Create a column that answers if a cell in one column is located in either of 4 other columns

Question

I want to create a column that answers if string values from column 'A' are in either column 'B' or 'C'. These can be converted to float or int if that makes it easier.

Data:
 A    B    C       OUTPUT
 A    B    C     No/False
 B    B    B     Yes/True
 A    A    C     Yes/True
 A    C    A     Yes/True

Answer 1

You can do

df["output"] = df.apply(lambda x: True if x["a"] in (x["b"], x["c"]) else False)

Answer 2

Let us try sin

df[['B','C']].isin(df.A).any(1)

0    False
1     True
2     True
3     True
dtype: bool