# I want to eliminate a list from a bigger list, only by typing something #

tasks = [] 
task = [task1,year,month,day, hour, minute, second, microsecond,str(cuando),cuando]# this is a list that is filed into another list named tasks#

# If I type a position, I want to eliminate a complete list that is filed in tasks #

tasks = [["math",year,month,day, hour, minute, second, microsecond]["biology",year,month,day, hour, minute, second, microsecond,str(cuando),cuando]]

# the program asks if you finished any tasks# 

k = 0
while k < CantTareas :
    ans = raw_input ("Did you finished any task? (yes or no) ")
    if ans == "yes":
        k = k + 1
        position = input ("which number of task did you finished? ) "

suppose that I say I finished position 0

[["math",year,month,day, hour, minute, second, microsecond]#this is position 0
["biology",year,month,day, hour, minute, second, microsecond,str(cuando),cuando]]#This is position 1

I want the program to print only the task or tasks I didn't finish

[["biology",year,month,day, hour, minute, second, microsecond,str(cuando),cuando]]

I think it is too cumbersome for user to enter number of task, if you do not print the tasks with number before asking them. Do not use input in Python2 it is too dangerous, use int(raw_input("prompt"))