How to split data into trainset and testset randomly?

Question

I have a large dataset and want to split it into training(50%) and testing set(50%).

Say I have 100 examples stored the input file, each line contains one example.

Answer 1

A quick note for the answer from @subin sahayam

 import random
 file=open("datafile.txt","r")
 data=list()
 for line in file:
    data.append(line.split(#your preferred delimiter))
 file.close()
 random.shuffle(data)
 train_data = data[:int((len(data)+1)*.80)] #Remaining 80% to training set
 test_data = data[int(len(data)*.80+1):] #Splits 20% data to test set

If your list size is a even number, you should not add the 1 in the code below. Instead, you need to check the size of the list first and then determine if you need to add the 1.

test_data = data[int(len(data)*.80+1):]