Syntax to select previous row in pandas after filtering

python pandas dataframe conditional-statements

Shift the mask up by 1.

df[(df['Value'] < 15).shift(-1).fillna(False)]   Row  Value1    2     25

More generally, if you're trying to find all rows greater than 15, whose next row is lesser than 15, you can compute two separate masks and AND them:

df[(df['Value'].shift(-1) < 15) & (df['Value'] > 15)]   Row  Value1    2     25

python pandas dataframe conditional-statements

`np.flatnonzero`

To find where the mask is True then subtract one

df.iloc[np.flatnonzero(df.Value < 15) - 1]   Row  Value1    2     25

python pandas dataframe conditional-statements

Using idxmax

>>> df.iloc[df.Value.le(15).idxmax() - 1]Row       2Value    25