How to apply random.uniform to two columns of a dataframe?

Question

How to apply random.uniform to two columns of a dataframe?

df = pd.DataFrame(np.random.randn(6,4),columns=list('ABCD'))

def f(x):
    return random.uniform(x[0],x[1])

df['E'] = f(df[['A','B']])

Answer 1

A vectorized approach would be:

df['E'] = (df.B - df.A) * np.random.rand(df.shape[0]) + df.A

Same as:

df['E'] = (df.B - df.A) * np.random.uniform(size=df.shape[0]) + df.A

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Timing 1 million rows

Don't use apply over large datasets if you can help it.