timer in python

import time, os

seconds_to_go_for = 10 # How long the timer will go for
current_time = int(time.time()) # Gets the time before the timer starts

def clear():
  if os.name == "nt":
    os.system("cls") # Clear function, to avoid spam. Source: geeksforgeeks.org
  else:
    os.system("clear")

while True:
  time_now = int(time.time()) # Gets time during the timer's running
  if time_now >= current_time + seconds_to_go_for: # Checks if enough time has passed
    break # Stops loop if so
  
  print(f"Seconds passed: {time_now - current_time}") # Prints how much time has passed
  clear()
print("The timer has ended") 

import time
timer_length = float(input("How many seconds would you like you're timer to be set for? "))
time.sleep(timer_length)
print("Done!")

timer = threading.Timer(interval, function, args = None, kwargs = None)
timer.start()

import time
import os

a = int(0)
b = int(0)

while True:
    print(str(b) + " minutes " + str(a) + " seconds")
    a += 1
    time.sleep(0.9999999)
    if a == 59:
        a = 0
        b += 1
    os.system('cls')

def hello():
    print "hello, world"

t = Timer(30.0, hello)
t.start() # after 30 seconds, "hello, world" will be printed