borehole   top  bottom  lithology
0     AP-2  94.6    95.1   dolomite
1     AP-2  95.1    96.7  limestone
2     AP-2  96.7    97.0   dolomite
3     AP-2  97.0    97.5  limestone
4     AP-2  97.5    97.8  limestone
5     AP-3  87.4    87.7  limestone
6     AP-3  87.7    88.1  limestone
7     AP-3  88.1    88.5   dolomite
8     AP-3  88.5    89.1  limestone

borehole   Top       Lith
0      AP-2  94.6   dolomite
1      AP-2  94.7   dolomite
2      AP-2  94.8   dolomite
3      AP-2  94.9   dolomite
4      AP-2  95.0   dolomite
5      AP-2  95.1  limestone
6      AP-2  95.2  limestone
7      AP-2  95.3  limestone
8      AP-2  95.4  limestone
9      AP-2  95.5  limestone
10     AP-2  95.6  limestone
11     AP-2  95.7  limestone
12     AP-2  95.8  limestone
13     AP-2  95.9  limestone
14     AP-2  96.0  limestone
15     AP-2  96.1  limestone
16     AP-2  96.2  limestone
17     AP-2  96.3  limestone
18     AP-2  96.4  limestone
19     AP-2  96.5  limestone
20     AP-2  96.6  limestone
21     AP-2  96.7  limestone

import pandas as pd
import numpy as np

liths = {'borehole': {0: 'AP-2',
  1: 'AP-2',
  2: 'AP-2',
  3: 'AP-2',
  4: 'AP-2',
  5: 'AP-3',
  6: 'AP-3',
  7: 'AP-3',
  8: 'AP-3'},
 'bottom': {0: 95.099999999999994,
  1: 96.700000000000003,
  2: 97.0,
  3: 97.5,
  4: 97.799999999999997,
  5: 87.700000000000003,
  6: 88.099999999999994,
  7: 88.5,
  8: 89.099999999999994},
 'lithology': {0: 'dolomite',
  1: 'limestone',
  2: 'dolomite',
  3: 'limestone',
  4: 'limestone',
  5: 'limestone',
  6: 'limestone',
  7: 'dolomite',
  8: 'limestone'},
 'top': {0: 94.599999999999994,
  1: 95.099999999999994,
  2: 96.700000000000003,
  3: 97.0,
  4: 97.5,
  5: 87.400000000000006,
  6: 87.700000000000003,
  7: 88.099999999999994,
  8: 88.5}}

filled = []
increment = 0.1
for row in liths.itertuples():
    start = row.top
    end = row.bottom
    for i in np.arange(start, end, increment):
        filled.append([row.borehole, i, row.lithology])
filled = pd.DataFrame(filled, columns=['borehole', 'Top', 'Lith']); filled