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pythondataframelambda

apply lambda condition on multiples if else condition

df['expens'] = df.apply(lambda z : z['total_bill'] * 2  if z['total_bill'] < 10 ,axis = 1)

I want to apply the lambda expression using the if condition and create new column variable df['expens'] under the condition if df['total_bill] is < 10

I tried the above the python syntax but is throws an error "invalid syntax"

Solution

  • Apply the condition during indexing, not in the lambda if you only want to apply the function to those rows for which the condition is true. Also no need for a lambda if just multiplying in pandas.

    df.loc[df["total_bill"]<10, "expens"] = df["total_bill"] * 2

    NB. it is possible to have a condition in a lambda with the ternary operator lambda x: x * 2 if x < 10 else x but not useful in this case.