# Let's assume we have a function that return current time, if we have the time as default value it will always show the same results:
import time

def show_time(current_time = time.ctime()):
  print(current_time)

# by calling the function show_time() withput arguments it will alwsays show same results
 show_time()
 #Sat Mar 16 12:26:42 2019
 show_time()
 #Sat Mar 16 12:26:42 2019
..

# again, this is happening because the default arguments evaluted only once at the time of creating the function.

#one solution is to call the function ctime() inside the function, and that way you evaluate on the function call.
def show_time(current_time = time.ctime):
  print(current_time()) #notice we are calling the time function

 show_time()
 #Sat Mar 16 12:27:30 2019
 show_time()
 #Sat Mar 16 12:27:31 2019