Conditional append list for Pandas dataframes

Question

I am using the following code to attempt to filter our specific rows but I am getting an error that says:

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

df = pd.DataFrame(rdataset)
plane = 'axial'
contrast = 'T1'

a = []

for slices in range(0,60):
    if df['nSlices']==slices:  #---------------> Problem here ?
        path = df.loc[df['nSlices'].eq(slices) & df['Orient'].eq(plane)  & df['Contrast'].eq(contrast),'Path'].tolist()
        a.append(path)

please show an example of your dataframe and your expected output — ansev
– ansev, Commented Dec 25, 2019 at 22:16

Stepan · Accepted Answer · 2019-12-26 00:54:50Z

1

The error appears because you are trying to compare Series object df['nSlices'] with scalar integer slices. The result of such comparsion is Series object with bool values (try to do print(df['nSlices']==slices) to see it) and you can't use it in if-statement.

To solve the problem just remove if df['nSlices']==slices: to get:

for slices in range(0,60):
    path = df.loc[df['nSlices'].eq(slices) & df['Orient'].eq(plane)  & df['Contrast'].eq(contrast),'Path'].tolist()
    a.append(path)

answered Dec 26, 2019 at 0:54

Stepan

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