Expanding pandas Data Frame rows based on number and group ID (Python 3).

Question

I have been struggling with finding a way to expand/clone observation rows based on a pre-determined number and a grouping variable (id). For context, here is an example data f

Answer 1

I can't replicate your index, but I can replicate your values, using np.repeat, quite easily in fact.

v = df.values
df = pd.DataFrame(v.repeat(v[:, -1], axis=0), columns=df.columns)

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If you want the exact index (although I can't see why you'd need to), you'd need a groupby operation -

def f(x):
    return x.astype(str) + '.' + np.arange(len(x)).astype(str)

idx = df.groupby('id').id.apply(f).values

Assign idx to df's index -

df.index = idx