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I'm trying to append certain columns of Pandas Data Frames from CSV files into a numpy array. I have no idea how to instantiate an empty numpy array, so I'm testing it first with a list.

def windows(files):
    x = []
    for my_files in files:
        with open(os.path.join("/Users", "saqibali", "PycharmProjects", "sensorLogProject", "Data", my_files),
              'rU') as my_file:
            df = pd.DataFrame(columns=['timestamp', 'time skipped', 'x', 'y', 'z', 'label']).set_index('timestamp')
            for d in sliding_window(sample_difference(my_file), 500, 250):
                df = df.append(d[['x', 'y', 'z']])
            x.append(df.values.toList())
    return x

I get the error in the title, and it doesn't make sense to me because x is a list and df is a Data Frame.

Answers

The method name is all lowercase: tolist.

So you need to change the offending line to:

x.append(df.values.tolist())