Python - How to get the last element of a list (no commas provided)

Question

I am working on a project with sensor data. I write the sensor data at first into a csv file to save it. After that I read the file and receive the sensor data as a list as follows:

[  0   1   1   0   0 516]
[  1   1   1   0   0 498]
[  2   1   1   0   0 499]
[  3   1   1   0   0 500]
[  4   1   1   0   0 487]
[  5   1   1   0   0 502]
...

There are no commas between the elements. I need the last element of this list to transfer the unit (analog data). I tested several things e.g. to create an array and convert it back to list and so on...

This is how I saved the data (working with a raspberry pi):

device.start(samplingRate, acqChannelsEDA)
    with open('/home/pi/pywork/EDAdata.csv', 'w') as edafile:
        # create csv writer
        writer = csv.writer(edafile)

        start = time.time()
        end = time.time()
        while (end - start) < running_time:
            # Read samples
            sampledata = device.read(nSamples)
           
            writer.writerow(sampledata)
            print(sampledata)
            # print(eda_tf)
            end = time.time()

    edafile.close()

The output for print(sampledata) is:

[[8 1 1 0 0 0]]
[[9 1 1 0 0 0]]
[[10  1  1  0  0  0]]
[[11  1  1  0  0  0]]
[[12  1  1  0  0  0]]
[[13  1  1  0  0  0]]
[[14  1  1  0  0  0]]
[[15  1  1  0  0  0]]

This is the code from read(self, nSamples=100). The method to get sampledata.

 dataAcquired = numpy.zeros((nSamples, 5 + nChannels), dtype=int)
            for sample in range(nSamples):
                Data = self.receive(number_bytes)
                decodedData = list(struct.unpack(number_bytes * "B ", Data))
                crc = decodedData[-1] & 0x0F
                decodedData[-1] = decodedData[-1] & 0xF0
                x = 0
                for i in range(number_bytes):
                    for bit in range(7, -1, -1):
                        x = x << 1
                        if (x & 0x10):
                            x = x ^ 0x03
                        x = x ^ ((decodedData[i] >> bit) & 0x01)
                if (crc == x & 0x0F):
                    dataAcquired[sample, 0] = decodedData[-1] >> 4
                    dataAcquired[sample, 1] = decodedData[-2] >> 7 & 0x01
                    dataAcquired[sample, 2] = decodedData[-2] >> 6 & 0x01
                    dataAcquired[sample, 3] = decodedData[-2] >> 5 & 0x01
                    dataAcquired[sample, 4] = decodedData[-2] >> 4 & 0x01
                    if nChannels > 0:
                        dataAcquired[sample, 5] = ((decodedData[-2] & 0x0F) << 6) | (decodedData[-3] >> 2)
                    if nChannels > 1:
                        dataAcquired[sample, 6] = ((decodedData[-3] & 0x03) << 8) | decodedData[-4]
                    if nChannels > 2:
                        dataAcquired[sample, 7] = (decodedData[-5] << 2) | (decodedData[-6] >> 6)
                    if nChannels > 3:
                        dataAcquired[sample, 8] = ((decodedData[-6] & 0x3F) << 4) | (decodedData[-7] >> 4)
                    if nChannels > 4:
                        dataAcquired[sample, 9] = ((decodedData[-7] & 0x0F) << 2) | (decodedData[-8] >> 6)
                    if nChannels > 5:
                        dataAcquired[sample, 10] = decodedData[-8] & 0x3F
                else:
                    raise Exception(ExceptionCode.CONTACTING_DEVICE)
            
            return dataAcquired

Answer 1

To get last element of a list, you should use negative indexing, e.g.

arr = [10, 20, 30, 40, 50]
print (arr[-1])
print (arr[-2])

Output:

50
40