python - How can I fill in a missing values in range with Pandas?

Question

I have a dataset with a number of values like below.

>>> a.head()
   value  freq
3      9     1
2     11     1
0     12     4
1     15     2

I need to fill in the values between the integers in the value column. For example, I need to insert one new row between 9 & 11 filled with zeroes, then another two between 12-15. The end result should be the dataset with 9-15 with 'missing' rows as zeroes across the board.

Is there anyway to insert a new row at an specific location without replacing data? The only methods I've found involve slicing the dataframe at a location then appending a new row and concatenating the remainder.

UPDATE: The index is completely irrelevant so don't worry about that.

Answer 1

You didn't say what should happen to your Index, so I'm assuming it's unimportant.

In [12]: df.index = df['value']

In [15]: df.reindex(np.arange(df.value.min(), df.value.max() + 1)).fillna(0)
Out[15]:
       value  freq
value
9          9     1
10         0     0
11        11     1
12        12     4
13         0     0
14         0     0
15        15     2