How can I calculate the variance of a list in python?

Question

If I have a list like this:

results=[-14.82381293, -0.29423447, -13.56067979, -1.6288903, -0.31632439,
          0.53459687, -1.34069996, -1.61042692, -4.032         


        

Answer 1

Without imports, I would use the following python3 script:

#!/usr/bin/env python3

def createData():
    data1=[12,54,60,3,15,6,36]
    data2=[1,2,3,4,5]
    data3=[100,30000,1567,3467,20000,23457,400,1,15]

    dataset=[]
    dataset.append(data1)
    dataset.append(data2)
    dataset.append(data3)

    return dataset

def calculateMean(data):
    means=[]
    # one list of the nested list
    for oneDataset in data:
        sum=0
        mean=0
        # one datapoint in one inner list
        for number in oneDataset:
            # summing up
            sum+=number
        # mean for one inner list
        mean=sum/len(oneDataset)
        # adding a tuples of the original data and their mean to
        # a list of tuples
        item=(oneDataset, mean)
        means.append(item)

    return means

# to do: substract mean from each element and square the result
# sum up the square results and divide by number of elements
def calculateVariance(meanData):
    variances=[]
    # meanData is the list of tuples
    # pair is one tuple
    for pair in meanData:
        # pair[0] is the original data
        interResult=0
        squareSum=0
        for element in pair[0]:
            interResult=(element-pair[1])**2
            squareSum+=interResult
        variance=squareSum/len(pair[0])
        variances.append((pair[0], pair[1], variance))

    return variances





def main():
    my_data=createData()
    my_means=calculateMean(my_data)
    my_variances=calculateVariance(my_means)
    print(my_variances)

if __name__ == "__main__":
    main()

here you get a print of the original data, their mean and the variance. I know this approach covers a list of several datasets, yet I think you can adapt it quickly for your purpose ;)