pandas dataframe根据列中的值删除后续行

Question

simple question but I have not been able to find anything on this. I have the following dataframe, and hope to accomplish the following:

where Roll = 1 in our dataframe, I want to delete the next row, and only that one row. Keep in mind that many rows for Roll will be 0 but only a few need to be removed specifically rows where the preceding row for Roll = 1

Date    Close    Open    Roll
1       500      499     0
2       502      502     0
3       500      499     0
4       500      499     1
5       501      502     0 (delete this row)
6       506      506     0
7       509      508     0

Answer 1

Create a boolean mask using shift that tests whether the previous row contains 1 or not:

In [24]:
df[df['Roll'].shift() != 1]

Out[24]:
   Date  Close  Open  Roll
0     1    500   499     0
1     2    502   502     0
2     3    500   499     0
3     4    500   499     1
5     6    506   506     0
6     7    509   508     0

the boolean mask looks like this:

In [25]:
df['Roll'].shift() != 1

Out[25]:
0     True
1     True
2     True
3     True
4    False
5     True
6     True
Name: Roll, dtype: bool