read large file using python?

Question

I want to read a.txt file which containing more than 25000 lines for that proposes I have written a python program, but it provided (output)only 490 lines can any one modify my program?

f = open('file2.txt','r')    
for line in f:    
 data=list(map(float,line.strip().split()))    
 y=[]    
 y.append(data[2])    
 print(y) 

Answer 1

If you want the 3rd float per line into the y list, you're looking for something like

y = []
with open("file2.txt") as f:
    for line in f:
        data = [float(x) for x in line.strip().split()]
        y.append(data[2])
print(y)