使用groupby.这至少应该比循环遍历所有行更有效率.

Use groupby. This should at least be more efficient than looping through all rows.

df = pd.DataFrame({'CarNumber': [303] * 4 + [404] * 2 + [405] * 5,
                   'othercol': range(11)})

def zero_row(cols, idx):
    return pd.DataFrame([[0] * len(cols)], columns=cols, index=[idx])

def add_zero_row(x):
    return x.append(zero_row(x.columns, x.index.max() + 0.5))

df = df.groupby('CarNumber').apply(add_zero_row)

# remove extra index from grouping
df = df.reset_index('CarNumber', drop=True)

# get rid of last zero row
df.iloc[:-1]